What does the calculator estimate?

It estimates ideal wheel output RPM from target speed and wheel diameter, plus a flat-floor rolling-torque screen per driven motor. The 0.05 rolling-resistance coefficient and 2× planning factor are assumptions, not DFRobot specifications. It does not certify motor fit.

Why does the calculator not say whether a DFRobot motor fits?

Robot mass alone cannot determine motor fit. Slope, acceleration, turning, wheel grip, gearbox efficiency, duty cycle, and thermal limits all affect the result. DFRobot lists stall torque for these examples but not a continuous torque rating, so compare a supplier-confirmed continuous rating and loaded speed before selecting a motor.

What are the listed FIT0186 motor specifications?

DFRobot lists FIT0186 as a 12 V, 43.8:1 gearmotor with 251 RPM no-load speed, 18 kg·cm stall torque, 7 A stall current, 350 mA no-load current, and 700 counts per gearbox-output revolution. These are catalog values; stall torque is not a continuous operating rating.

What are the listed FIT0403 motor specifications?

DFRobot lists FIT0403 as a 12 V, 90:1 gearmotor with 122 RPM no-load speed, 38 kg·cm stall torque, and 7 A stall current. Its wiki specification table says 1,440 counts per gearbox-output revolution, while the introduction says 5,756; confirm the count convention and exact motor revision with DFRobot before using it for odometry.

Is the listed no-load speed the speed I will get on my robot?

No. The listed speed is a no-load catalog value. A wheel under load will run slower, and the public FIT0186/FIT0403 pages do not include a full speed-torque curve. Ask for the curve or measure speed on the assembled robot.

What is the trade-off between FIT0186 and FIT0403?

The listed FIT0186 ratio is 43.8:1 with 251 RPM no-load speed and 18 kg·cm stall torque; FIT0403 is 90:1 with 122 RPM and 38 kg·cm stall torque. This suggests a slower, higher stall-torque option versus a faster one, but the figures do not establish continuous performance or gearbox life.

How deep can the mounting screws go?

DFRobot warns that screws can hit the gearbox and recommends no more than 3 mm of screw penetration into the mounting holes. Check the actual bracket and screw length before assembly.

Can I connect the encoder directly to a 3.3 V controller?

DFRobot lists a 5 V encoder operating voltage but does not specify output-level compatibility for every controller. Check the exact electrical interface; if the controller input is not 5 V tolerant, use a suitable level shifter or interface circuit.

How should I size the motor driver and supply?

The listed stall current is 7 A per motor. Do not treat that as continuous current, but do account for startup, jams, current limiting, wiring, battery sag, and driver thermal limits. The public product pages do not provide a continuous-current rating, so request it or validate the duty cycle with measurements.

What should I confirm with a supplier before ordering?

Request the loaded speed-torque curve, continuous torque/current and thermal limits, duty-cycle and gearbox-life guidance, encoder count convention and electrical interface, and the current drawing for shaft and mounting dimensions. Confirm availability and lead time separately because those details can change.

When should I consider a planetary gearmotor?

Compare the required continuous output torque, loaded speed, shock loads, duty cycle, environment, backlash, and service life with documented ratings for each candidate. There is no universal robot-weight cutoff; request a planetary candidate specification when the DFRobot product data leaves a critical requirement unverified.

Does a 12 V motor automatically provide more torque than a 6 V motor?

No. Voltage by itself does not determine output torque or suitability. Match the motor winding, gearbox, driver, and battery to the required speed, continuous torque, current, and thermal duty.

Planetary Gear Motor

Robot drive sizing · Published 26 September 2026 · Updated 7 October 2026 · Sources checked 6 October 2026

DFRobot 12V DC Motor: Wheel RPM & Torque Calculator

Screen the wheel speed and a flat-floor torque estimate for your robot, then compare the result with published FIT0186 and FIT0403 data. The calculator does not make a motor-fit or payload verdict.

Robot inputs

Total robot mass (kg)

0.1–1,000 kg total robot mass

Loaded wheel diameter (mm)

10–1,000 mm loaded wheel diameter

Target ground speed (m/s)

0.01–20 m/s target speed

Number of driven motors

1–16 driven motors; use a whole number

Drivetrain screening result

Targets for the inputs shown; no automatic product-fit verdict is inferred.

146.9

Ideal wheel output RPM

From target ground speed and wheel circumference; actual speed depends on load and tire slip.

0.03

N·m per driven motor

Flat-floor rolling estimate with a 2× planning factor (0.3kg·cm).

Screening only

Assumes a level, hard floor, rolling-resistance coefficient 0.05, equal torque sharing, and a 2× planning factor. It excludes slope, acceleration, turning, gearbox losses, shock, and thermal limits. Compare against a supplier continuous-torque rating and loaded-speed curve; stall torque alone cannot confirm a fit.

Request a motor match

What the published data can tell you

Use these catalog values for an initial comparison. They do not replace continuous-duty ratings, a loaded motor curve, or a test on the target robot.

No universal weight cutoff

Robot mass alone cannot establish suitability. Wheel size, acceleration, grade, tire grip, number of driven wheels, duty cycle, and gearbox limits change the required output torque.

Treat stall data carefully

Both example models list 7 A stall current. That is not a continuous-current rating. Check the driver, current limit, supply, wiring, and thermal behavior for the actual duty cycle.

Check mounting and encoder data

DFRobot limits FIT0186 screw penetration to 3 mm. The FIT0403 wiki gives different output-encoder counts in its introduction and specification table, so confirm the count convention before closing an odometry design.

DFRobot 12V model comparison

Manufacturer listings checked 6 October 2026. “No-load” and “stall” values describe test endpoints; neither is a continuous operating point.

Published specifications for DFRobot FIT0186 and FIT0403 12V gearmotors
Model	Ratio	No-load output speed	Stall torque	Stall current	Output encoder counts	Continuous torque
FIT0186	43.8:1	251 RPM (listing: +10%)	18 kg·cm	7 A	700 counts/rev	Not published; confirm with supplier
FIT0403	90:1	122 RPM (±10%)	38 kg·cm	7 A	1,440 in specification table; 5,756 in introduction — verify	Not published; confirm with supplier

These listings provide stall torque and current, not a continuous torque curve or gearbox life rating. Do not use stall torque as a normal running target or infer a robot payload limit from it.

How to interpret the calculator

Speed estimate

wheel RPM = target speed ÷ (π × loaded wheel diameter) × 60

This is the ideal wheel output speed for the entered ground speed. Compare it with a candidate’s speed under load, not its no-load catalog speed.

Flat-floor torque screen

torque per motor = mass × g × 0.05 × wheel radius ÷ driven motors × 2

The 0.05 rolling-resistance coefficient and 2× factor are illustrative assumptions. Include grade, acceleration, turning, gearbox efficiency, and measured traction for a real design.

Missing a loaded-speed curve or continuous-duty rating? Request a supplier data review before choosing a motor.

Request a data review

Encoder and driver checks before wiring

Keep motor power and logic signals distinct. Confirm the exact pinout and signal levels for the selected revision before powering the system.

Driver and supply

The listed 7 A stall current is per motor. Select current limiting, battery, driver, connector, and wiring for the expected startup and jam behavior; confirm thermal limits under the intended duty.

Encoder and mounting

DFRobot lists a 5 V encoder supply, but signal-level tolerance depends on the controller. Protect non-5-V-tolerant inputs. For FIT0186, do not screw more than 3 mm into the mounting holes.

Sources and evidence limits

Published by Planetary Gear Motor. The specifications below come from the cited DFRobot listings; this page is a software screening aid and does not claim a physical motor test or customer result. About the publisher.

DFRobot FIT0186 product specification
Speed, gear ratio, stall torque/current, encoder count, and 3 mm mounting-depth warning. Checked 6 October 2026.
DFRobot FIT0403 product wiki
Speed, ratio, stall torque/current, encoder supply and counts. The page itself conflicts on output counts; verify before control or odometry calculations. Checked 6 October 2026.
DFRobot mobile-robot torque calculation tutorial
Background for force-to-wheel-torque screening. The coefficient and planning factor in this calculator are stated assumptions, not values from the motor datasheets.

Frequently asked questions

12V DC motor for a robot: sizing calculator 12V gearmotor ratio and drive-wheel selection 12-volt robot motor selection and trade-offs

Need a motor match for your robot?

Share the target speed, wheel size, duty cycle, and available supply. An engineer can help identify the ratings that still need confirmation.

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