A hydraulic actuator can be the right pressure, the right brand, and the right price, yet still be the wrong choice for the application. Proper sizing often serves as the determining factor for whether a hydraulic system is able to deliver the force, speed, reliability, and service life it was designed to achieve. From bore and rod diameter to stroke, pressure, mounting, and duty cycle, every specification matters.

For engineers, OEMs, system designers, and maintenance professionals, hydraulic actuator sizing is an essential step in building a system that performs reliably under real operating conditions. Getting it right requires looking beyond a single specification and understanding how the actuator interacts with the rest of the hydraulic and mechanical system.

At Supreme Integrated Technology, we understand that hydraulic actuators are a vital part of the complete system. SIT designs and manufactures custom hydraulic power units, valve automation systems, and integrated hydraulic solutions for a variety of demanding applications across industrial, marine, defense, civil, and subsea markets.

This guide covers seven important factors to consider when sizing a hydraulic actuator.

1. Determine the Required Force

The first step in hydraulic actuator sizing is determining how much force the actuator must produce to move or hold the load.

At a basic level, the relationship is: Force = Pressure × Area

Because piston area increases with bore diameter, a larger cylinder bore will produce more force at the same hydraulic pressure.

However, the required actuator force should not be based solely on the weight of the load. The calculation may also need to account for friction, gravity, mechanical advantage, acceleration, external forces, and the way the load is connected to the actuator.

For example, a cylinder lifting a load vertically may need to generate more force than the load’s static weight because the application may introduce friction, mechanical losses, or dynamic forces during movement.

How do you calculate hydraulic cylinder force?

Force = Pressure × Area

In order to estimate the force produced during cylinder extension, multiply hydraulic pressure by the piston area. During retraction, the effective area is smaller because the piston rod occupies part of the cylinder area.

This difference means a cylinder does not necessarily produce the same force in both directions. Extension and retraction force should therefore be evaluated separately when the application requires force in both directions.

At SIT, actuator decisions are evaluated within the context of the overall hydraulic system. Its custom hydraulic power units are designed around application-specific operating requirements and can incorporate pumps, reservoirs, controls, cooling, and other system components as needed.

Once the required force is established, the next step is determining how much hydraulic pressure is available to produce it.

2. Select the Appropriate Operating Pressure

Pressure and actuator size are closely connected. A cylinder operating at higher pressure can generally produce the required force with a smaller bore, while a lower-pressure system may require a larger bore to achieve the same output.

When selecting an actuator, it is vital to consider both the system’s normal operating pressure and its maximum pressure. Important pressure considerations include:

• Normal working pressure
• Maximum system pressure
• Pressure spikes and transient conditions
• Relief valve settings
• Pressure losses through valves, piping, hoses, and fittings
• Pressure ratings of the actuator and associated components

What pressure should a hydraulic cylinder be rated for?

A hydraulic cylinder should be specifically rated for the maximum pressure it is expected to encounter, including applicable transient conditions. The design should also consider the pressure rating of the complete hydraulic circuit rather than looking at the cylinder in isolation.

It is important not to assume that operating a cylinder at a system’s maximum available pressure is always the best approach. Hydraulic actuator sizing should not be based only on theoretical minimum force. The design should account for dynamic forces, friction, pressure losses, appropriate safety factors, duty cycle, and the complete mechanical system.

The actuator should be sized to meet the actual force requirement at the intended operating pressure, while maintaining appropriate design margins and ensuring that all components are compatible.

A properly sized hydraulic actuator works within the system’s intended pressure range rather than relying on excess pressure to compensate for an undersized design.

3. Determine the Required Stroke Length

Stroke length is the distance the hydraulic actuator must travel to complete its intended movement.

Choosing the correct stroke is critical. A cylinder with insufficient stroke may not reach the required position, while an unnecessarily long cylinder can increase equipment size, cost, and installation requirements.

To determine the required stroke, evaluate:

• Starting position
• Ending position
• Required equipment travel
• Linkage and pivot geometry
• Available installation space
• Clearance throughout the full range of motion

One important consideration is that actuator stroke does not always equal the final movement of the equipment. Lever arms, pivots, linkages, chain-and-pulley arrangements, and other mechanical systems can change the relationship between cylinder travel and equipment movement.

SIT’s project experience includes custom actuation systems where mechanical arrangements allow equipment to achieve a greater range of motion than the actuator’s physical stroke alone. For example, a SIT-designed cargo lift platform uses mechanically coupled actuation and a chain-pulley system to achieve a 120-inch target range using a single 60-inch actuator stroke.

How do you determine hydraulic cylinder stroke length?

Determine the actual mechanical travel required by the application, then account for the linkage, mounting points, and range of motion to calculate the actuator stroke needed to produce that movement.

Stroke should be verified against the complete mechanical design rather than selected solely from a catalog.

4. Calculate Required Actuator Speed and Flow

Force determines whether a hydraulic actuator can move the load. Flow determines how quickly it moves. 

If more flow is supplied to a cylinder, the actuator moves faster. However, the required flow also depends on cylinder bore because a larger piston has more area and therefore requires more fluid to travel at the same speed.

How do you calculate hydraulic cylinder speed?

Cylinder Speed = Flow ÷ Effective Area 

Hydraulic cylinder speed can be estimated by dividing flow by effective piston area:

For cylinders with different extension and retraction areas, the required flow and resulting velocity will differ between directions.

For example, a cylinder may extend at one speed and retract at another even when the same pump flow is supplied, because the rod reduces the effective area on the rod side.

Flow requirements should also be evaluated at the system level. Pumps, valves, hoses, filters, heat exchangers, and other components must be capable of supporting the required flow without creating excessive pressure losses or heat.

This is one reason actuator sizing should not be treated as an isolated component-selection exercise. The actuator must work within the capabilities of the hydraulic power unit and control system supplying it.

SIT’s hydraulic power units can be configured with hydraulic and electrical controls, cooling systems, motor starters, and other components to support application-specific system requirements.

5. Evaluate Mounting Geometry, Alignment, and Side Loads

A cylinder’s dimensions may look correct on paper, but improper mounting or alignment can create significant mechanical problems.

Hydraulic cylinders are generally intended to apply force along their centerline. When the actuator experiences side loads, bending forces, or misalignment, additional stress can be placed on the rod, bearings, seals, mounting hardware, and surrounding structure.

Before selecting an actuator, evaluate:

• Mounting style
• Pin locations
• Clevis or trunnion arrangements
• Flange or foot mounting
• Pivot requirements
• Centerline alignment
• Side loading
• Load distribution throughout the stroke

Can a hydraulic cylinder handle side loads?

Hydraulic cylinders should not generally be relied upon to absorb significant side loads unless the cylinder and system are specifically designed for those forces.

External guides, properly designed linkages, or other mechanical structures may be required to keep the load aligned with the actuator.

Mounting geometry can also influence cylinder length and stroke requirements. The correct cylinder for a particular application may therefore be very different from what a simple force calculation suggests.

This is particularly important in large industrial equipment, marine systems, movable structures, and other applications where actuators may be exposed to complex loading conditions.

SIT has experience integrating hydraulic cylinders and actuation systems into custom equipment, including movable structures and other applications where mechanical, hydraulic, and control requirements must work together.

6. Consider Duty Cycle and Operating Environment

An actuator that cycles a few times per hour has very different operating requirements from one that runs continuously.

Duty Cycle

When sizing a hydraulic actuator, consider:

• Number of cycles per hour
• Cycle frequency
• Time under load
• Continuous versus intermittent operation
• Expected service life
• Operating temperature
• Heat generation

Higher duty cycles can increase heat generation and component wear, making proper sizing and system cooling especially important.

Operating Environment

The environment surrounding the actuator can also affect material and component selection.

Consider whether the actuator will operate in:

• Outdoor environments
• Marine or offshore environments
• Saltwater exposure
• High or low temperatures
• Dust or contamination
• Corrosive atmospheres
• Washdown environments
• Hazardous areas

Environmental conditions may influence rod materials, coatings, seals, mounting hardware, protection requirements, and other specifications.

SIT’s work spans demanding environments and applications, including marine, offshore, defense, civil infrastructure, industrial, and subsea systems. Its experience includes custom systems designed around application-specific operating conditions and duty requirements.

For example, SIT has developed hydraulic systems incorporating cooling, filtering, load-sense control, and other features to support continuous operation in demanding applications.

The actuator therefore needs to be selected not just for what it can do under ideal conditions, but for what it must withstand throughout its expected service life.

7. Size the Rod and Verify Mechanical Requirements

Selecting the cylinder bore is only part of hydraulic actuator sizing. The piston rod must also be appropriately sized for the mechanical loads it will encounter.

Rod diameter can affect:

• Compression strength
• Buckling resistance
• Stability
• Bearing loading
• Side-load sensitivity
• Available retraction force

Why is hydraulic cylinder rod diameter important?

A hydraulic cylinder rod must be strong enough to withstand the mechanical loads generated during operation. Long cylinders operating in compression may be particularly susceptible to buckling, making unsupported length, mounting configuration, and load conditions important considerations.

Rod diameter also affects hydraulic performance. Because the rod occupies part of the piston area, a larger rod reduces the effective area on the retraction side and therefore changes the cylinder’s retraction force and speed characteristics.

How do you determine hydraulic cylinder rod size?

Rod sizing should be based on the expected mechanical load, cylinder geometry, unsupported length, mounting arrangement, and operating conditions. Compression loading and buckling should be evaluated as part of the mechanical design rather than selecting a rod diameter based only on the cylinder bore.

For demanding applications, this verification step is essential. A cylinder may have sufficient hydraulic force capacity but still be unsuitable if its rod, mounting, or mechanical configuration cannot safely handle the applied load.

Hydraulic Actuator Sizing: A Step-by-Step Process

Proper hydraulic actuator sizing can be approached systematically:

1. Determine the required force: Calculate the force needed to move or hold the load, accounting for friction, gravity, mechanical advantage, acceleration, and other applicable forces.

2. Identify the operating pressure: Determine the pressure the actuator will normally operate at and verify the maximum pressure it may experience.

3. Calculate the preliminary bore size: Use the required force and pressure to determine the minimum piston area and corresponding bore.

4. Determine stroke length: Calculate how far the actuator must travel based on the actual mechanical movement and mounting geometry.

5. Calculate speed and flow requirements: Use the desired actuator velocity and effective piston area to determine the hydraulic flow required.

6. Verify mounting and alignment: Check mounting style, pivot points, side loads, mechanical alignment, and the surrounding structure.

7. Verify rod size and operating conditions: Evaluate buckling, compression, duty cycle, environment, temperature, and expected service life.

These calculations provide the starting point for actuator selection. Final sizing should be validated against the complete hydraulic and mechanical system.

Hydraulic Actuator Sizing Example

Consider a simplified application requiring a hydraulic cylinder to produce a specified linear force at a known operating pressure.

The first calculation is piston area:

A = F ÷ P

Once the required piston area is known, the corresponding theoretical bore diameter can be calculated from the piston-area relationship.

The next step is to select an appropriate practical cylinder bore. The calculated diameter may not correspond to an available standard cylinder size, so the design may require selecting the next suitable bore and then verifying the resulting performance.

From there, evaluate:

• Required stroke
• Extension force
• Retraction force
• Desired extension and retraction speeds
• Required pump flow
• Rod diameter
• Buckling resistance
• Mounting configuration
• Duty cycle
• Environmental conditions

This process demonstrates why hydraulic actuator sizing is more involved than simply matching a cylinder to a pressure rating.

For custom hydraulic systems, these calculations also need to be considered alongside the hydraulic power unit, valves, controls, reservoir, cooling, filtration, and other components.

Common Hydraulic Actuator Sizing Mistakes

Even a technically sound hydraulic system can experience problems when actuator sizing is based on incomplete information.

Sizing only by pressure

A pressure rating does not tell you whether a cylinder can produce the required force. Bore size and effective piston area are equally important.

Ignoring retraction force

The rod reduces effective piston area during retraction, so retraction force is lower than extension force for a typical single-rod cylinder at the same pressure.

Forgetting side loads

Misalignment and side loading can contribute to premature wear and mechanical problems even when the cylinder’s hydraulic force rating is sufficient.

Choosing the wrong stroke

An actuator that is too short may not provide the required movement, while an unnecessarily long stroke can increase space, cost, and installation requirements.

Ignoring duty cycle

The operating frequency and duration of the actuator can affect heat generation, wear, and expected service life.

Selecting the bore without verifying the rod

Hydraulic force capacity alone does not confirm that the cylinder can withstand the mechanical loading associated with the application.

Treating the actuator as an isolated component

The actuator needs to work with the pump, valves, controls, fluid, piping, mounting structure, and other components in the system. A cylinder that looks appropriate by itself may not be the right choice for the complete system.

When Should You Use a Custom Hydraulic Actuator?

Standard hydraulic cylinders can be appropriate for many applications, but some projects require specifications that do not fit an off-the-shelf configuration.

A custom actuator or custom-integrated hydraulic system may be appropriate when an application involves:

• Non-standard dimensions
• Unique mounting requirements
• Unusual stroke lengths
• High-force requirements
• Tight space constraints
• Harsh environmental conditions
• Complex control requirements
• Specialized duty cycles
• Equipment retrofits
• Integration with a custom hydraulic power unit

SIT’s capabilities include custom hydraulic power units, hydraulic and electro-hydraulic control systems, valve automation, and integrated hydraulic solutions. Its published project experience also includes custom hydraulic components and actuation systems for demanding applications.

For a project with complex requirements, the right approach may be to design the actuator and hydraulic power system together rather than selecting individual components independently.

How SIT Supports Custom Hydraulic System Requirements

Hydraulic actuator sizing is only one part of developing a reliable hydraulic system. The actuator must ultimately work as part of a coordinated power, control, and mechanical package.

SIT designs and builds custom hydraulic power units and integrated hydraulic and electro-hydraulic systems around application-specific requirements. Its capabilities include hydraulic and electrical controls, valve automation, assembly, testing, commissioning, and field support.

SIT’s Houston manufacturing operation supports HPU assembly, while the company’s quality management system is ISO 9001:2015 certified. SIT also offers factory acceptance testing capabilities, including remote participation for customers.

That system-level perspective can be especially valuable when an application involves multiple actuators, custom controls, tight space requirements, demanding duty cycles, or specialized operating environments.

Frequently Asked Questions About Hydraulic Actuator Sizing

What is hydraulic actuator sizing?

Hydraulic actuator sizing is the process of determining the appropriate actuator specifications for an application, including force capacity, bore, rod diameter, stroke, pressure rating, speed, flow requirements, mounting configuration, and environmental requirements.

How do you size a hydraulic actuator?

To size a hydraulic actuator, determine the required force, operating pressure, stroke, speed, flow, mounting geometry, duty cycle, and mechanical loading. These factors are then used to select and verify the appropriate bore, rod diameter, stroke, and pressure rating.

How do you calculate hydraulic cylinder force?

Hydraulic cylinder force is calculated by multiplying hydraulic pressure by effective piston area. Extension and retraction force differ when the cylinder has a single piston rod because the rod reduces the effective area during retraction.

How do I calculate hydraulic cylinder bore size?

Begin by dividing the required force by the available hydraulic pressure to determine the required piston area. The piston area can then be used to calculate a theoretical bore diameter. The selected cylinder should then be verified against practical dimensions, available sizes, mechanical requirements, and operating conditions.

Can hydraulic cylinders handle side loads?

Hydraulic cylinders are generally intended to apply force along their centerline. Significant side loads should be addressed through appropriate mechanical design, alignment, guides, or other means rather than relying on the cylinder to absorb them.

When should I consider a custom hydraulic actuator or system?

Custom solutions may be appropriate when an application has non-standard dimensions, specialized mounting, unusual force or stroke requirements, tight space constraints, demanding environments, complex controls, or other requirements that standard components cannot adequately address.

How can SIT help with hydraulic system requirements?

SIT provides custom hydraulic power units and integrated hydraulic and electro-hydraulic systems for demanding applications. Its capabilities include system manufacturing, controls, testing, commissioning, and field support within its product and system scope.

Bottom Line? Start With the Application, Not the Cylinder

Proper hydraulic actuator sizing starts with understanding the application.

Force, pressure, stroke, speed, flow, mounting geometry, rod size, duty cycle, and environmental conditions all influence the final actuator selection. Looking at only one specification can result in an actuator that technically fits the system but does not deliver the performance, reliability, or service life the application requires.

For straightforward applications, a systematic sizing process can provide a strong starting point. For more complex systems, actuator selection should be evaluated alongside the hydraulic power unit, controls, mechanical structure, and operating environment.

Need help sizing a hydraulic actuator or designing a hydraulic system around your application? Contact SIT to discuss your force, stroke, speed, pressure, and control requirements.