Updated Jan 31, 2026
PTO Generator Calculator
Size a PTO generator or estimate required PTO horsepower using load mix, buffer, PTO speed, and efficiency.
Reviewed by SuperCalc Engineering
Calculator Inputs
Estimated Results
Planning estimate (not a final spec)
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How PTO generator sizing works
PTO generators convert tractor horsepower into electrical power. A simple conversion is kW = PTO HP x 0.746 x efficiency. We then apply a surge factor for motor loads and a buffer for temperature, altitude, and future growth.
In reverse mode, enter the running load in kW to estimate the PTO horsepower needed to handle both running and surge loads.
Typical PTO generator ranges
- 540 RPM: common for 10-60 kW generators
- 1000 RPM: common for 25-120 kW generators
- Match PTO speed and shaft type before purchase
Example calculation
FAQ
How do I size a PTO generator?
Start with the tractor PTO horsepower and convert to kW using HP × 0.746 × efficiency. Then add a buffer and a surge factor for motor-heavy loads.
What is the difference between 540 and 1000 RPM PTO?
They are different PTO speed standards. Many smaller generators target 540 RPM, while larger units often use 1000 RPM. Your tractor and generator must match.
How much buffer should I add?
A 10-20% buffer is common for temperature, altitude, and future load growth. Motor-heavy loads may need more surge margin.
Is this a running load or surge load estimate?
This calculator estimates both: running kW and a surge-adjusted kW using a load mix factor.
Can I use this for standby sizing?
Yes, it provides a planning estimate, but confirm with equipment specs and a licensed electrician for critical installations.