Tractor PTO Horsepower Calculator

Inputs

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Use shaft torque for PTO-driven implements. Use draft pull for a drawbar-power screen from pull force and ground speed.
Measured or estimated torque required at the implement input shaft.
lbf·ft
Implement input speed. Common PTO speeds are 540 and 1000 rpm, but use the actual shaft speed.
rpm
Power transfer efficiency. Use PTO driveline efficiency for shaft mode, or drawbar/traction allowance for draft mode.
%
Extra power allowance after efficiency losses.
%
Rated or measured PTO power available from the tractor at the relevant engine/PTO speed.
hp
Reference PTO speed used to convert required power into equivalent torque.
rpm

Results

Default result
Edit inputs
Required PTO power(P_req)
39.41hp
Pass

Net implement power divided by efficiency, then increased by the entered margin.

Also computed

Net implement power(P_net)30.84hp

Shaft power = torque x RPM x 2*pi/60 before the entered efficiency and margin.

PTO power margin(P_avail - P_req)Pass10.59hp

Positive margin against the entered available PTO power.

PTO utilization(U)Pass78.83%

Required PTO power divided by available PTO power.

Torque at rated PTO speed(T_ref)383.3lbf·ft

Torque that would transmit the required power at the entered rated PTO speed.

Efficiency used(eta)0.9

Entered drive efficiency: 90.0%.

Margin used(m)0.15

Entered power margin: 15.0%.

Tractor / implement power preview tool 39.4 hp required 383 lb-ft at rated PTO speed
Method notes 3 notes
  • Shaft power = torque x RPM x 2*pi/60 before the entered efficiency and margin.
  • Draft mode reports an equivalent power screen; drawbar horsepower is not the same rating as PTO horsepower.
  • Final tractor/implement matching still needs manufacturer recommendations, Nebraska Tractor Test data where relevant, gear range, ballast, traction, tire load, hydraulics, terrain, crop/soil conditions and implement condition.

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