Motor Torque Chart

Use this worksheet after the calculator result to record power, RPM, full-load torque, starting torque, breakdown torque, required load torque, slip, and torque margin.

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Quick reference table

A motor torque chart is a calculator worksheet for the mechanical side of motor selection. It connects HP and RPM to shaft torque, then keeps full-load torque, starting torque, breakdown torque, load torque, and duty notes separate before the motor, gearbox, or VFD package is checked.

Torque result worksheet

Torque result worksheet
Torque item	Record from calculator	Field use before the next decision
Rated power	HP or kW	Confirm mechanical output basis
Speed	RPM and angular velocity	Confirm motor speed, gearbox output, or driven-equipment speed
Full-load torque	Calculated shaft torque	Compare with steady load torque
Starting torque	Starting torque estimate or manufacturer value	Check acceleration requirement
Breakdown torque	Peak available torque	Check overload and stall margin
Slip or margin	Slip and torque margin	Use for motor, gearbox, or VFD package check

Load torque behavior cues

Load torque behavior cues
Load type	What to record	Why the chart is different
Conveyor or positive-displacement pump	High starting or breakaway torque	Starting torque can matter more than running HP
Fan or centrifugal pump	Torque change with speed	VFD speed changes can sharply change load demand
Hoist, lift, or vertical load	Holding torque, brake, and duty notes	Mechanical safety factors live outside the simple HP formula
Gearbox output	Motor RPM and output RPM separately	Torque after gearing is not the same as motor shaft torque

Formula basis

Torque lb-ft = HP x 5252 / RPM. Torque N-m = kW x 9550 / RPM.

HP or kW is the mechanical power basis selected in the calculator.
RPM is the motor, gearbox output, or driven-equipment speed used for the torque result.
Full-load torque is the running torque at rated output and speed.
Torque margin compares available torque with required load torque during running and starting conditions.

Worked examples

Low-speed conveyor checkA conveyor may have acceptable running HP but high breakaway torque, so the worksheet keeps starting torque and load torque beside the calculator result before motor selection.

VFD fan speed changeA fan running at reduced RPM changes both power and torque demand, so the chart records speed, torque, and duty notes before drive settings are treated as final.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The worksheet assumes the calculator power and RPM basis match the actual motor, gearbox, or driven-load condition.
Starting torque, breakdown torque, and load torque are planning values until checked against manufacturer curves or drive settings.
Mechanical service factors, brakes, couplings, shafts, belts, and gearbox ratings are outside the simple torque formula and should be checked separately.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart for motor selection planning; verify nameplate data, load torque curve, drive settings, manufacturer data, equipment ratings, and AHJ requirements where applicable.

How to use this chart

1Pair power with speedRecord HP or kW and RPM together because torque cannot be interpreted correctly without both values.

2Separate torque typesKeep full-load, starting, breakdown, and required load torque separate so the next selection step is clear.

3Check the marginUse the torque margin field to decide whether manufacturer curves, VFD limits, gearbox data, or mechanical load data need checking.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Record rated valuesWrite rated power, rated speed, calculated torque, and synchronous-speed or slip notes from the calculator.
Record load valuesDocument required load torque, acceleration needs, duty cycle, breakaway torque, and any mechanical service factor assumptions.
Record package checksList whether the result points to motor selection, gearbox ratio, VFD setup, coupling rating, brake check, or a manufacturer torque curve.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Comparing motor HP alone while ignoring the RPM that controls delivered shaft torque.
Using full-load torque as a starting-torque guarantee without checking the load curve and manufacturer motor data.
Forgetting that gearbox output torque, motor shaft torque, and driven-equipment torque may be three different values.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Why does torque increase when RPM decreases?

For the same mechanical horsepower, torque is inversely related to speed, so a lower RPM can deliver more torque at the shaft.

Is full-load torque enough for starting a load?

No. Starting loads may need more torque during acceleration, so starting torque, breakdown torque, drive limits, and the load curve must be checked.