How to Measure and Calculate the Stroke Length You Actually Need

Stroke is the single most common sizing mistake in linear actuator projects — and the most expensive one, because an actuator with the wrong stroke cannot be adjusted into correctness. Too short, and your hatch never fully opens, your TV never clears the cabinet, or your platform never reaches height. Too long, and the actuator bottoms out, binds, or will not fit when retracted. This guide shows how to measure the stroke you actually need, before you order.

First, Three Lengths You Must Not Confuse

Stroke length is the distance the rod travels, from fully retracted to fully extended. If an actuator has a 200 mm stroke, the rod tip moves 200 mm between its two end positions. That is all stroke means.

Retracted length is the total length of the actuator when the rod is fully in — body plus rod end, end to end. This decides whether the actuator fits in your space when closed.

Installed length (sometimes called mounting distance) is the distance between the two mounting points — the fixed base bracket and the moving load bracket — at a given position. It changes as the actuator moves: at full retraction it is at its shortest, at full extension at its longest. The difference between those two installed lengths is the stroke you need.

A useful check: stroke = installed length at full extension − installed length at full retraction. If you remember nothing else, remember that subtraction.

Method 1: Measure the Movement Directly

This works when the moving part travels in a straight line and you can reach both end positions — a vertical lift, a sliding drawer, a straight push.

  1. Put the moving part in its closed (or lowered) position. Mark a fixed reference point on the moving part and a matching point on the frame.
  2. Move it by hand to its open (or raised) position.
  3. Measure the distance between the two marks. That distance is the minimum stroke.

Then add margin. Do not order a stroke exactly equal to this measurement: brackets, hinges, cable slack, and small build tolerances all eat into it. Choose the next stroke option above your measurement (see “Choosing the Stroke” below).

Method 2: Measure the Two Mounting Distances

This is the method for hinged lids, trapdoors, hatches, and anything that swings on a pivot — where the actuator does not push in a straight line with the load.

  1. Decide where the two brackets will go: one fixed point on the frame, one on the moving part. Mark both. The bracket positions matter as much as the stroke, because moving a bracket a few centimetres changes the geometry.
  2. With the moving part closed, measure the straight-line distance between the two bracket points. This is the closed installed length.
  3. With the moving part open to its target position, measure the same two points again. This is the open installed length.
  4. Subtract: open installed length − closed installed length = required stroke.

Work through this with the brackets in their real positions, not in your head. On a hinged lid, the actuator’s own angle changes through the travel, so a stroke that looks right at the midpoint can be wrong at either end. If the two positions are hard to reach by hand, mock the brackets up with cardboard or scrap timber first and check the full swing before drilling anything. Also check the retracted fit at the same time: with the part closed, is there room for the actuator’s full retracted length between the brackets, plus the brackets themselves? A stroke can be perfect and the actuator still impossible to install because its body is longer than the closed space.

When the Actuator Is Mounted at an Angle

An actuator rarely pushes straight up. More often it pushes at an angle, and only part of its stroke becomes useful movement in the direction you care about. The rule is simple geometry: the useful movement in your target direction is the stroke multiplied by the cosine of the angle between the actuator and that direction. In plain terms, the more angled the actuator, the less of its stroke counts toward the lift.

Worked example (geometry only, not a product specification): suppose you need 150 mm of vertical lift, and the actuator will sit at 30° from vertical. The stroke you need is 150 ÷ cos(30°) ≈ 150 ÷ 0.866 ≈ 173 mm. So a 150 mm stroke would fall short; you need a stroke above 173 mm, and then you still add the margin described below. If the angle is steep — say 60° from vertical — the same 150 mm of lift needs 150 ÷ cos(60°) = 300 mm of stroke. That is why a lid actuator mounted almost flat to the frame needs a surprisingly long stroke.

Two practical consequences. First, measure the angle at the position where it matters most (usually the closed position, where the actuator is flattest and weakest). Second, remember that the angle changes as the part moves: check the geometry at both ends of the travel, not just in the middle.

Choosing the Stroke: The Rule

  1. Measure the required stroke by Method 1 or Method 2 above.
  2. Take the next available stroke option above your measurement — never the one just below it, and never exactly equal if you can avoid it. The margin covers bracket thickness, hinge play, and the fact that real builds are never as exact as drawings.
  3. Check the retracted length fits in the closed position.
  4. Check the extended length does not drive the moving part past its stop, into a wall, or beyond its hinges. Built-in limit switches stop the actuator at the ends of its stroke, but they cannot protect a hinge that is being forced past its design range — the mounting geometry has to be right first.

If your measurement falls between two stroke options and the larger one will not fit when retracted, the answer is not to force it: move a bracket, change the mounting angle, or split the job. A stroke that fits retracted and covers the travel is worth more than a stroke that looks tidier on paper.

Common Stroke Mistakes

  • Measuring only one position. You need both the closed and the open distance. One number alone tells you nothing.
  • Ordering exactly the measured stroke. With no margin, the first build tolerance eats your travel and the lid stops short.
  • Confusing stroke with total length. A “300 mm actuator” in conversation usually means 300 mm of stroke, but its retracted body is longer. Always check both numbers on the product page’s Full Specifications.
  • Forgetting that brackets move too. On a hinge, the load-side bracket swings on an arc. A straight-line subtraction at the midpoint is not the same as the true travel at the ends.
  • Ignoring clearance at full extension. Cables, hinges, and neighbouring panels all need room at the open position, not just at rest.
  • Picking stroke before picking brackets. Bracket placement changes the required stroke. Fix the brackets first, then measure, then order.

A Quick Pre-Order Checklist

  • ☐ Closed installed length measured between real bracket points
  • ☐ Open installed length measured at the target position
  • ☐ Required stroke calculated (open − closed)
  • ☐ Mounting angle checked at both ends of travel
  • ☐ Next stroke option above the measurement selected
  • ☐ Retracted length fits in the closed space
  • ☐ Full extension does not over-travel the hinge or stop
  • ☐ Force rating checked separately against the real load (stroke does not decide force)

FAQ

Can I limit a too-long stroke with the controller instead of buying the right stroke? Not reliably. Built-in limit switches stop the actuator at its own stroke ends. Stopping it early every cycle with external controls or by cutting power mid-travel is a workaround, not a design — and it leaves the extended length problem unsolved. Buy the right stroke.

What if my measurement is between two stroke options? Take the larger one, provided it fits when retracted. If it does not fit, change the bracket geometry before you order, not after.

Does stroke affect speed or force? Not directly. Speed and force are set by the motor and gearing of the model you choose. Stroke only sets how far the rod travels. Check speed and force separately on the model’s product page.

I already bought an actuator and the stroke is short. What now? First check the brackets: moving the load-side bracket further from the hinge increases the travel for the same stroke, up to a point — but it also increases the force the actuator must deliver. If the geometry cannot be fixed, the honest fix is the correct stroke, not a longer lever that overloads the motor.

Should I measure with the load attached? Yes, whenever you can. An unloaded lid, hatch, or platform sits differently from a loaded one, and hinges sag under weight. Measure in the loaded state if the load is already built.

The Short Version

Stroke is travel, not total length. Measure both end positions between real bracket points, subtract, allow for the mounting angle, and order the next size up. Do that before you drill a single hole, and the actuator will arrive as a solution instead of a return.

Still choosing the actuator? Start with the linear actuator selection guide, then read our power supply sizing guide and our guide to wiring a linear actuator. For a concrete build that lives or dies by its stroke, see our DIY TV lift cabinet guide.

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