Calculate stall torque from Kt and current or estimate it from voltage, resistance, and Kv. View results in N-m, N-cm, kg-cm, oz-in, lb-in, or lb-ft.
Assumptions & Formulas
– From Kt & Current: Stall Torque (Ts) = Torque Constant (Kt) × Stall Current (Is)
– From Voltage, Resistance & Kv: Stall Torque (Ts) = (9.5488 / Kv) × (Voltage (V) / Resistance (R))
Definitions:
– Stall Torque: The maximum torque a motor can deliver when the rotational speed is zero (i.e., the motor is stalled or locked).
– Torque Constant (Kt): A measure of the torque produced by an electric motor per unit of current drawn.
Note: The Voltage & Resistance method provides an ideal theoretical estimate of stall torque. It assumes a direct connection without accounting for motor controller current limits, wiring voltage sag, or increased resistance due to winding temperature rise under stall conditions. Results are mathematically precise based on the inputs and rounded to 4 decimal places.
This stall torque calculator finds a motor’s maximum torque using either the torque constant and stall current, or the supply voltage, armature resistance, and Kv. The result can be shown in N-m, N-cm, kg-cm, oz-in, lb-in, or lb-ft. The voltage, resistance, and Kv method provides an ideal mathematical estimate, not a measured real-world stall test.
How This Stall Torque Calculator Works
The calculator uses two distinct paths to determine maximum motor torque. The direct path multiplies the motor’s torque constant (Kt) by the current drawn at stall. The secondary path estimates torque from basic electrical specifications by calculating the theoretical stall current from voltage and resistance, converting the speed constant (Kv) to a torque constant, and then multiplying those derived values.
Stall Torque Formula Used in This Calculator
This tool relies on specific formulas depending on the selected calculation path.
For the direct method using torque constant and current:$$Stall\ Torque = Kt \times Stall\ Current$$
For the estimation method using basic motor specifications, the tool follows a step-by-step sequence:$$Stall\ Current = \frac{Voltage}{Resistance}$$$$Kt = \frac{9.5488}{Kv\ (in\ RPM/V)}$$$$Stall\ Torque = Stall\ Current \times Kt$$
Formulas Used by the Tool
| Step | Formula |
|---|---|
| Direct method | Stall Torque = Kt × Stall Current |
| Specs method: stall current | Stall Current = Voltage ÷ Resistance |
| Specs method: torque constant | Kt = 9.5488 ÷ Kv (in RPM/V) |
| Specs method: final torque | Stall Torque = Stall Current × Kt |
Input Methods in This Calculator
| Method | Inputs required | What the tool does |
|---|---|---|
| From Torque Constant (Kt) & Current | Torque constant, stall current | Multiplies Kt by stall current to calculate stall torque |
| From Voltage, Resistance & Kv | Supply voltage, armature resistance, Kv | Calculates stall current from voltage and resistance, derives Kt from Kv, then calculates stall torque |
Supported Input and Output Units
| Item | Units supported |
|---|---|
| Torque constant (Kt) | N-m/A, N-cm/A, kg-cm/A, oz-in/A, lb-in/A, lb-ft/A |
| Stall current | A, kA, mA |
| Kv | RPM/V, rad/s/V |
| Result torque | N-m, N-cm, kg-cm, oz-in, lb-in, lb-ft |
Voltage, Resistance, and Kv Assumptions
The calculation based on voltage, resistance, and Kv provides an ideal theoretical estimate. It assumes a direct electrical connection and constant winding temperature. This mathematical result does not account for motor controller current limits, voltage drop in the wiring, or the natural increase in electrical resistance caused by rapid heating under stall conditions.
When to Use Each Input Method
Use Torque Constant (Kt) & Current when you already know the motor’s torque constant and stall current. Use Voltage, Resistance & Kv when you need an ideal stall torque estimate from basic electrical motor specifications.
FAQ
What is the formula for stall torque?
For the direct method, stall torque is calculated as torque constant × stall current.
Can I estimate stall torque from voltage, resistance, and Kv?
Yes. This calculator estimates stall current from voltage ÷ resistance, converts Kv into Kt, and then calculates stall torque from those derived values.
What is the difference between Kt and Kv in this calculator?
Kt is the motor torque constant used to calculate torque from current. Kv is the motor speed constant; in the second method, the calculator converts Kv into Kt before calculating stall torque.
Why is the voltage, resistance, and Kv result only an estimate?
That method assumes an ideal electrical path and does not account for controller current limits, voltage sag, or resistance increase from heating at stall.
What units can I use in this stall torque calculator?
The calculator supports Kt units of N-m/A, N-cm/A, kg-cm/A, oz-in/A, lb-in/A, and lb-ft/A; current units of A, kA, and mA; Kv units of RPM/V and rad/s/V; and result torque units of N-m, N-cm, kg-cm, oz-in, lb-in, and lb-ft.
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