Servo Motor Sizing Calculator
Peak and RMS torque from your move profile — inertia, acceleration time and duty cycle, with the inertia-ratio check built in.
Pick a servo whose RATED torque ≥ RMS and PEAK (typically 3× rated) ≥ T(peak). Keep the inertia ratio under ~10:1 for snappy tuning (under 30:1 workable with modern drives); above that the loop oscillates. Don't forget gravity on vertical axes — a constant torque added to friction, and you may need a brake.
Servo Sizing Calculator computes peak and RMS torque a servo axis needs from its motion profile — free, instant and private in your browser. Automation engineers selecting servos and drives for positioning axes use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Servo Motor Sizing Calculator
Servo Sizing Calculator computes peak and RMS torque a servo axis needs from its motion profile using the standard engineering relation: T(peak) = J·α + T(friction); T(RMS) = √(Σ Ti²·ti/Σti) over the cycle. Worked live: 9.2 kg·cm² total inertia accelerated to 3000 RPM in 0.1 s demands ~2.9 N·m peak. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Servo Motor Sizing Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Servo Motor Sizing Calculator?
- ✓Implements the real formula — T(peak) = J·α + T(friction) — with the substitution shown, not a black box
- ✓Built for automation engineers selecting servos and drives for positioning axes
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate servo sizing?+
Peak and RMS torque a servo axis needs from its motion profile follows T(peak) = J·α + T(friction); T(RMS) = √(Σ Ti²·ti/Σti) over the cycle. For example, 9.2 kg·cm² total inertia accelerated to 3000 RPM in 0.1 s demands ~2.9 N·m peak. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why do servo datasheets list rated AND peak torque?+
Thermal vs magnetic limits: rated torque is what the motor sustains forever; peak (typically 3× rated) is available for seconds during acceleration. Your RMS demand must fit under rated, your acceleration spikes under peak — both checks, not either.
What inertia ratio should I aim for?+
Under 10:1 load:motor tunes crisply; modern drives manage 30:1 with stiff couplings; beyond that the motor cannot dominate the load and the loop oscillates or crawls. Gearing helps quadratically — doubling the ratio quarters the reflected inertia.
Is the Servo Sizing Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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