Start with loaded speed
ratio = rpm in ÷ rpm out
Use the motor shaft speed at the required load. A no-load speed can overstate the output speed once the application is connected.
Calculate the required ratio and output power, then verify the result against the motor curve and gearhead datasheet.
Request an engineering reviewDecision Summary
ratio = rpm in ÷ rpm out
Use the motor shaft speed at the required load. A no-load speed can overstate the output speed once the application is connected.
P = T × 2πn ÷ 60
At a fixed 1,000 rpm, more requested torque means proportionally more mechanical output power. Compare that point with the gearhead continuous operating range.
Catalog ratios vary
Available ratios, stage counts, input-speed limits, and torque-speed envelopes belong to a specific gearhead series and configuration.
Worked catalog example
The examples below use maxon GPX 10 catalogue configurations and assume exactly 1,000 rpm at the output. Required motor speed is output speed × ratio. They illustrate the check; they are not a recommendation or a claim about other gearheads.
| Catalog configuration | Motor speed for 1,000 rpm out | Max continuous input speed | Max continuous transmitted power | What to conclude |
|---|---|---|---|---|
| GPX 10, 1 stage, 4:1 | 4,000 rpm | 12,000 rpm | 1.6 W | The calculated input speed is below the catalog input-speed limit. The operating-range curve still needs checking at the requested torque. |
| GPX 10, 2 stages, 16:1 | 16,000 rpm | 12,000 rpm | 1.2 W | This ratio would require input speed above the catalog continuous limit for a 1,000 rpm output. |
Catalog maxima are separate limits, not a guarantee that a specific torque-speed point is continuously allowable. Check the full operating-range plot and the motor curve. The sizer's default 50 mN·m at 1,000 rpm requires 5.24 W at the output, above the GPX 10 continuous power limits shown here (1.6 W for one stage and 1.2 W for two). This table screens ratio and input speed; it does not show that either configuration meets that default torque. Originally published September 26, 2026; page method reviewed October 6, 2026. Source: maxon GPX 10 catalogue, 2025 edition, accessed October 6, 2026. Open manufacturer catalogue
Selection checklist
| Check | Why it matters | Ask for this evidence |
|---|---|---|
| Motor operating speed under load | The output speed follows the actual motor speed divided by the selected reduction ratio. | Motor speed-torque curve or a measured operating point at the intended voltage and load. |
| Exact ratio and stage configuration | Gearheads offer discrete ratios; the mathematical ratio from the sizer may not be a catalog option. | A matching gearhead configuration and its rated input-speed limit. |
| Continuous torque and power at speed | A maximum torque value alone does not show that the same torque is allowed at 1,000 rpm continuously. | The manufacturer’s continuous operating-range plot for the chosen ratio and version. |
| Duty cycle, temperature, and shaft loads | Intermittent ratings and permissible radial or axial loads can differ from continuous-use limits. | Application-specific thermal, duty, mounting, and bearing-load limits from the product data. |
Decision rule: accept a candidate only when its loaded motor speed, actual available ratio, and continuous gearhead operating range meet the same application point. If any item is unknown, request the datasheet or a supplier-confirmed operating point before ordering samples.
Boundaries and risks
The selected ratio may miss 1,000 rpm after the application torque pulls motor speed down.
Mitigation: Size from the loaded speed point on the motor curve, then confirm the complete motor and gearhead operating point.
A supplier may not offer that exact ratio, or its input-speed limit may rule out the required operating point.
Mitigation: Compare nearby catalog ratios and calculate the resulting loaded output speed for each candidate.
Peak or intermittent torque can exceed the continuous range at the requested speed and duty cycle.
Mitigation: Check continuous torque and transmitted power together on the selected gearhead’s operating-range plot.
Overhung radial load, axial load, or misalignment can exceed the output bearing limits even when speed and torque fit.
Mitigation: Include coupling, shaft geometry, load distance, and mounting alignment in the supplier review.
FAQ
Divide the motor shaft operating speed under load by 1,000 rpm. For example, 4,000 rpm at the motor shaft gives a theoretical 4:1 reduction. The selected catalog ratio may differ, so calculate the resulting output speed from the actual ratio.
Only if 12,000 rpm is the motor speed under the required load, the gearhead offers that ratio, and the gearhead permits that continuous input speed. Verify all three against the motor and gearhead data.
Output mechanical power is torque in N·m multiplied by angular speed in rad/s. At 1,000 rpm, 10 mN·m corresponds to about 1.05 W at the output shaft. The motor must supply more input power because the drive has losses.
No. It calculates the theoretical reduction, output power, and ideal input torque from your values. It does not check a specific motor curve, catalog ratio, thermal limit, or gearhead operating-range plot.
Voltage is included in the inquiry details for matching a motor winding and controller. Voltage alone does not determine loaded motor speed or available torque; those depend on the specific motor and operating conditions.
The ratio equation is the same. The usable motor speed and torque must come from the selected motor’s data at the intended voltage, controller, load, and duty cycle.
No. Life and noise depend on the specific motor, gearhead design, materials, lubrication, load, mounting, and test conditions. Request comparable supplier data for the exact configuration.
Send target loaded output speed and torque, voltage, duty cycle, size limits, radial or axial load, noise or backlash needs, annual volume, and application details. Include a motor speed-torque curve or drawing if available.
Next step
Share your loaded motor speed, output torque, voltage, duty cycle, and size limits. Ask the supplier to confirm the available ratio and continuous torque-speed range for the exact configuration.
Inquiry Email
Include OD/length, voltage, torque, loaded speed, ratio, drawings, quantity, and destination.
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