In Short
- How much bore does it take for how many tons of force? How thick should the rod be? The steps for correct sizing, and the mistakes that get expensive.
- Topics covered in this article: Why Sizing Matters So Much, Force Table by Bore and Pressure, Pull Force: Don't Forget the Rod Cross-Section, Rod Buckling: The Hidden Risk of a Long Stroke, Speed and Flow Relationship.
- Our services related to this topic: Hidrolik Silindir İmalatı, Hidrolik Güç Ünitesi İmalatı, Kromlu Mil ve Honlanmış Boru.
- On-site inspection is free within and around Izmir; a firm quote follows measurement.
In This Article9 sections
Why Sizing Matters So Much
A hydraulic cylinder is a part that operates under high pressure. A poorly sized cylinder doesn't just fail to do its job — it creates a safety risk. On the other hand, an oversized cylinder means unnecessary investment and a bigger, more expensive power unit to drive it.
Correct sizing starts with four pieces of information: required force, available pressure, travel distance, and desired time. Once those four are given, bore, rod diameter and required flow can all be calculated.
Force Table by Bore and Pressure
In a hydraulic cylinder, force is piston area multiplied by system pressure. Approximate theoretical push force at different pressures for common bores:
| Bore | 100 Bar | 160 Bar | 250 Bar | 320 Bar |
|---|---|---|---|---|
| Ø40 mm | ~1.3 t | ~2.0 t | ~3.1 t | ~4.0 t |
| Ø50 mm | ~2.0 t | ~3.1 t | ~4.9 t | ~6.3 t |
| Ø63 mm | ~3.1 t | ~5.0 t | ~7.8 t | ~10.0 t |
| Ø80 mm | ~5.0 t | ~8.0 t | ~12.6 t | ~16.1 t |
| Ø100 mm | ~7.9 t | ~12.6 t | ~19.6 t | ~25.1 t |
| Ø125 mm | ~12.3 t | ~19.6 t | ~30.7 t | ~39.3 t |
| Ø160 mm | ~20.1 t | ~32.2 t | ~50.3 t | ~64.3 t |
| Ø200 mm | ~31.4 t | ~50.3 t | ~78.5 t | ~100.5 t |
The table shows the same force can be reached two ways: a larger bore at lower pressure, or a smaller bore at higher pressure. Which is right depends on the situation:
- If space is tight, high pressure + small bore is preferred.
- If the existing power unit runs at low pressure, the bore needs to be larger.
- Higher pressure demands better sealing quality and thicker wall sections; it raises cost.
Pull Force: Don't Forget the Rod Cross-Section
When a cylinder pushes, the full piston area is at work; when it pulls, the rod cross-section is subtracted from that area. That's why pull force is always lower than push force.
The gap depends on the ratio of rod diameter to piston diameter. A thin rod means less pull loss but more buckling risk; a thick rod improves buckling safety but noticeably reduces pull force.
If your application does its work by pulling (opening a cover, retracting a mechanism, for example), the calculation must be done for the pull direction. Skip this detail and the cylinder pushes just fine but falls short when pulling — something we run into often on site.
Rod Buckling: The Hidden Risk of a Long Stroke
In a long-stroke cylinder, the rod behaves like a column under a pushing load and tends to bow past a certain load level. This isn't a gradual failure — once the limit is exceeded, the rod bends suddenly and the cylinder becomes unusable.
Factors that raise buckling risk:
- Long stroke combined with a thin rod
- High push force
- Single-point mounting (cantilevered)
- The load off the cylinder axis
- The cylinder left extended horizontally for long periods
The fix is a larger rod diameter, supporting the cylinder at two points, or a different mounting type. If you have a long-stroke application, mention it upfront — we'll size the rod diameter accordingly.
Speed and Flow Relationship
How fast the cylinder moves is set by the oil flow delivered to it. The logic is simple: the larger the cylinder's internal volume and the shorter the time the move needs to take, the more litres per minute are required.
This calculation works both ways:
- Once the cylinder is chosen, the required flow is calculated and the power unit is sized around it.
- If a cylinder is being added to an existing unit, that unit's flow determines the cylinder's speed.
A common mistake: choosing a large cylinder and connecting it to a small existing unit. The cylinder produces force, but motion ends up unacceptably slow. That's why the cylinder and the power unit have to be assessed together — since we manufacture both in the same workshop, we build that compatibility in from the start. See details on our power unit manufacturing page.
Material and Surface Quality
Sizing isn't just about picking dimensions — material decisions are made at this stage too:
| Component | Standard Choice | Demanding Environment |
|---|---|---|
| Body tube | Honed steel tube | Stainless or coated tube |
| Piston rod | Ground + hard chrome plated | Stainless or heavier chrome plating |
| Caps | Steel / cast | Stainless material |
| Sealing | NBR / polyurethane | FKM, PTFE or environment-specific |
| Fasteners | Galvanised bolts | Stainless bolts and nuts |
Choosing cheaper material saves a little on the cylinder itself, but it's expensive against the hours the machine sits idle. A cylinder built with an unhoned tube or a thin-chrome rod runs fine for the first few months, then starts leaking. We've covered this in detail on our chrome-plated rods and honed tubes page.
6 Common Sizing Mistakes
The most common sizing mistakes we see on site, and their consequences:
- Not accounting for pull direction: the cylinder works fine pushing but falls short pulling. The reason is simple: the rod cross-section is subtracted from the area when pulling, reducing force. If the work is done pulling, size for that direction.
- Skipping rod buckling: the force calculation is correct, but on a long-stroke cylinder the rod ends up too thin. It bows under load and the cylinder is scrapped.
- Not stating the speed requirement: ask for "a power unit to run this cylinder" and the resulting system produces force but moves far slower than expected.
- Not knowing the real line pressure: the pump might put out 200 bar, but if only 160 bar remains by the end of the line, the calculation comes out wrong.
- Leaving no safety margin: a cylinder sized right at the limit fails as soon as pressure dips slightly or friction increases.
- Underestimating the environment: "inside the factory" isn't enough detail. Washdown, chemicals, temperature and dust completely change the material and seal choice.
All of these mistakes are avoidable by asking the right questions. You don't need to do the math yourself, but knowing what's being asked makes it easier to evaluate the solution you're offered.
Pre-Order Checklist
To pin down the right cylinder quickly, have this information on hand — it's fine if some is missing, we'll fill in the gaps during inspection:
- Required force: how many kg / tons will it push or pull?
- Direction: pushing, pulling, or both?
- Stroke: how many mm of travel?
- Time: how many seconds should the move take?
- System pressure: what does the existing unit run at?
- Mounting: foot, flange, clevis?
- Rod end: threaded, clevis, or custom?
- Environment: moisture, chemicals, temperature, dust?
- Cycle rate: how many movements per day/hour?
You don't need to fill in this list yourself. Bring in your sample cylinder or send us photos of it — we'll take the measurements. The most practical way is WhatsApp: send us a message.
Frequently Asked Questions
What pressure range do you manufacture cylinders for?
The 100-250 bar range common in industry is routine work for us; special requests needing higher pressure are calculated with matching material and wall thickness. Every cylinder is tested and delivered at a test pressure above its working pressure.
My existing unit runs at 160 bar — should I size my cylinder to that?
Yes. The existing unit's pressure and flow determine both the cylinder's force and its speed. Tell us your unit's specs and we'll size the cylinder to match; we'll also suggest improvements to the unit side if needed.
What should I watch out for with a long-stroke cylinder?
The most critical issue is rod buckling. On a long stroke, the rod diameter should be chosen thicker than what force alone would calculate. Mounting type (two-point support, clevis connection) and keeping the load on-axis also become important.
Is it worth having the cylinder and power unit made together?
Yes. Pressure, flow and speed compatibility are built in from the start when they're designed together; you avoid problems like 'plenty of force but too slow' or 'fast but weak' showing up later. You also deal with a single point of contact.
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This content was prepared by our technical team at our workshop in Konak, Izmir, based on hands-on manufacturing, repair and overhaul experience with hydraulic and pneumatic cylinders.
Last updated: August 27, 2026