Free online linear actuator sizing calculator
ModuSystems AI is a free linear actuator sizing calculator that runs in the browser. Type the task — "2.5 kg, 500 × 500 mm, 500 mm/s pick and place" — and in about a minute it returns the required motor torque, the inertia mismatch, the torque and speed margins on real motor curves, the cycles per minute, the catalog actuators and controller that meet the spec with list prices, and a 3D assembly you can export as STEP. No account, no spreadsheet, no waiting for a quote.
What you enter
Five numbers, or just a sentence. Payload in kg — everything the carriage moves, including the tool. Travel in mm for each axis. Speed in mm/s. System type — single axis, XY, XYZ, H-gantry or dual-X gantry with Z. Optionally orientation (vertical adds gravity torque) and acceleration time (0.25 s default). If you leave something out, the engine states the assumption it made in one line so you can correct it.
What it calculates
| Output | What it means | Rule applied |
|---|---|---|
| Required torque | Acceleration + gravity + thrust torque at the motor shaft, at your speed | Belt: pulley circumference per rev · Screw: lead per rev |
| Torque margin | Available torque at that rpm from the motor's curve ÷ required | ≥ 25%, read from catalog curves (stepper 24 V, servo 48 V) |
| Inertia mismatch | Load inertia reflected to the motor ÷ rotor inertia | ≤ 10:1 on belt axes; gearbox remedy computed when exceeded |
| Family sweep | Every motor in the frame size, with margin and mismatch | Smallest motor that passes both wins |
| Load gate | Catalog rated load vs payload | Rated ≥ 2 × payload, hard gate |
| Move profile | Move time, out-and-back cycle, cycles per minute | Trapezoidal profile with your accel time |
| Parts and price | Actuator SKUs, gearbox, controller, options | Live catalog list prices |
| Comparison | Stepper vs servo side by side | Both sized from the same spec; price delta per axis |
An example, start to finish
Input: XY system, 2.5 kg, 500 × 500 mm, 500 mm/s, stepper. Output, about 40 seconds later: moving mass on X 4.97 kg (payload plus the 2.47 kg Y actuator); motor speed 23.07 rev/s; required torque 5.75 oz-in; family sweep on NEMA 17 — N17-1 fails inertia at 12.5:1, N17-2 at 11.0:1, N17-3 selected at 291% torque margin and 8.2:1, N17-4 passes but is larger than needed; speed margin 48%; move time 1.25 s, 24 cycles/min; parts: two SBA45 500 mm stepper actuators with the integral 3:1 gearbox at $1,800 each and a BLC-2T controller at $795. The 3D model builds in the viewer as the numbers print, and one click emails the BOM with STEP links to your inbox.
Why it is different from a sizing spreadsheet
A spreadsheet or a motor vendor's calculator stops at torque. This one starts there and finishes the job: it picks the actual actuator variant (travel, motor, gearbox, encoder) from a 100-SKU catalog, checks the load rating with a safety factor, selects the controller by axis count and motor type, prices the whole system, and builds the assembly in 3D so you can see the envelope and export it to CAD. Because the engine is deterministic and shows its inputs, the result is a specification you can hand to a colleague, not a black-box recommendation. And when a request is outside the catalog, it says so in numbers — "1,880 mm requested, 1,275 mm maximum" — and hands the design to an engineer from inside the same chat.
Who it is for
Design and automation engineers sizing a pick-and-place, a Z lift, a test fixture or a lab gantry; integrators who need a budgetary quote with a drawing before the kickoff meeting; and anyone who has ever sized a stepper on its holding torque and found out at commissioning that it stalls at speed. The guides below explain the method the engine runs, if you want to check it by hand.
Open the calculator — free
Describe the task in a sentence or fill in the five numbers. The engine sizes the motors, builds the 3D system, selects the controller and prices it, with every number shown.
Frequently asked
Is the linear actuator sizing calculator really free?
Yes. Sizing, the 3D build, the stepper-vs-servo comparison, the quote and the STEP export are free and need no account. An account is only used to save quotes and place orders.
What inputs does it need?
Payload (kg), travel (mm) per axis, speed (mm/s), and the system type — single axis, XY, XYZ or a gantry. Orientation and acceleration time are optional; the engine assumes horizontal and 0.25 s unless you say otherwise.
What does it calculate?
Required torque at the motor (acceleration, gravity and thrust terms), reflected inertia and the inertia-mismatch ratio, torque and speed margin against real motor curves, a sweep of every motor in the family, the gearbox remedy when mismatch exceeds 10:1, move time and cycles per minute, and the catalog parts with list prices that meet the result.
How accurate is it?
The sizing engine is deterministic — the same inputs always give the same numbers — and reads motor torque from catalog curves (stepper pull-out curves at 24 V, servo continuous curves at 48 V) rather than nameplate values. It enforces a 2× load safety factor and a 25% torque margin, and shows every number it used so you can check it.
Can I use it for a multi-axis gantry?
Yes. Describe an XY, XYZ, H-gantry or dual-X gantry with a Z axis and it sizes every axis, includes the stacked actuator masses, selects the controller and builds the 3D assembly. Limits: 1,500 mm per axis, 50 kg payload (servo), 2,500 mm/s.
Does it compare stepper and servo?
Ask "stepper or servo?" and it sizes both from the same spec on real torque data, side by side, with the price difference per axis.
Can I export the result?
Yes — STEP files of the actuators and assembly, a priced bill of materials, a quote, and the motion program as Snap2Motion, Python, G-code or C++. The system you build can be emailed to you with a link that reopens it.
What if my application is outside the catalog?
The engine builds to the nearest limit, states the gap in millimetres or kilograms, and offers to hand the design to a ModuSystems engineer from inside the chat. You get a sized proposal within one business day.