Inputs
Example data table
| Max torque (N·m) | Reach (m) | Offset (m) | Tool mass (kg) | Dynamic | Safety | Max payload (kg) | Proposed payload (kg) | Status |
|---|---|---|---|---|---|---|---|---|
| 120 | 0.75 | 0.10 | 3.50 | 1.30 | 1.25 | ≈ 7.82 | 7.00 | PASS |
| 80 | 0.90 | 0.15 | 4.00 | 1.40 | 1.30 | ≈ 0.16 | 2.00 | FAIL |
Formula used
This calculator sizes payload using a torque balance around the limiting joint. It treats the payload and tooling as a combined load acting at an effective lever arm.
- Effective lever = reach + COM offset
- Torque required = (payload + tooling) × g × lever × dynamic
- Allowable total mass = torque_max ÷ (g × lever × dynamic × safety)
- Max payload = allowable total mass − tooling
Dynamic factor approximates acceleration and shocks; safety factor adds conservative margin.
How to use this calculator
- Enter the maximum wrist or joint torque limit from the datasheet.
- Measure reach to the flange and add payload center offset.
- Include all tooling mass attached to the flange.
- Set dynamic factor based on motion aggressiveness and impacts.
- Pick a safety factor to match your engineering standards.
- Press Calculate Payload and review PASS/FAIL and margins.
- Download CSV/PDF for design reviews and change control.
Load capacity depends on lever arm
Payload rating is strongly shaped by distance. When reach is 0.75 m and payload COM offset is 0.10 m, the effective lever becomes 0.85 m. With 120 N·m maximum torque and a dynamic factor of 1.30, the same mass produces higher torque as the lever grows, so a small offset change can remove kilograms of capacity.
Dynamic factor captures motion stress
Acceleration, sudden stops, cable drag, and part slosh can amplify forces. A dynamic factor of 1.10 suits gentle moves, while 1.40 may fit fast cycles or impacts. In the example above, moving from 1.30 to 1.40 increases required torque by about 7.7%, directly reducing allowable mass.
Safety factor protects against uncertainty
Safety factor adds conservative margin for manufacturing variation, wear, and modeling error. Many teams use 1.10 for prototypes and 1.25 to 1.50 for production. Because allowable total mass divides by safety factor, increasing it from 1.25 to 1.40 lowers the permitted mass by 10.7%.
Tooling mass is part of the load
Grippers, brackets, sensors, and hoses consume payload budget. If tooling is 3.5 kg and allowable total mass at the flange is 11.3 kg, the maximum part mass is only 7.8 kg. Reducing tooling by 0.5 kg immediately returns 0.5 kg to the payload limit.
Use utilization to compare options
Torque utilization percent helps compare layouts. If a proposed 7.0 kg part with 3.5 kg tooling needs 113 N·m, utilization is 94%. Swapping to a lighter tool or shortening offset can drop utilization below 85%, improving uptime and lowering joint temperature.
Exported results support reviews
CSV exports suit spreadsheets and design logs, while PDF reports fit approvals and maintenance records. Include the torque limit source, reach measurement method, and chosen factors. Keeping consistent exports makes it easier to trace changes when a cell, fixture, or motion profile is updated. Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document Document
FAQs
1) Does this replace the manufacturer payload chart?
No. It is a conservative estimator for early design checks. Always confirm with the robot datasheet, orientation limits, inertia constraints, and any vendor-specific derating rules.
2) What should I use for dynamic factor?
Start with 1.10 for slow, smooth moves. Use 1.20–1.35 for typical cycles. Use 1.40+ when there are impacts, rapid stops, cable drag, or uncertain acceleration profiles.
3) Why is COM offset important?
Offset increases the lever arm, so torque rises linearly with distance. Even 0.05 m extra offset can noticeably reduce safe payload, especially at long reach and higher dynamic factors.
4) Why can max payload become negative?
If tooling mass alone exceeds allowable total mass, the computed payload margin turns negative. Reduce tooling, shorten reach/offset, lower dynamic factor, or select a robot with higher torque capacity.
5) What margins should I target?
Many teams aim for 10–20% torque headroom for thermal and wear margin. Higher margins are common for 24/7 duty cycles, harsh environments, or uncertain part variation.
6) What is included in the CSV/PDF exports?
Exports include all inputs and key outputs: lever arm, allowable total mass, maximum payload, required torque, utilization, pass/fail, and margins. Use them for design reviews, documentation, and change control.