Tractor Drawbar Pull from Power

The drawbar pull a tractor develops at a working speed for a given power.

Run the calculator

Example

You enter

Power (hp) 75
Power basis pto
Ground speed (mph) 4.5
Surface firm_soil

You get

Drawbar pull 4500 lb

Details, formula, and sources

pull = 375 x drawbar_hp / speed (a PTO rating converts first with drawbar_hp = pto_hp x tractive efficiency). A 75 PTO-hp tractor at 4.5 mph on firm soil (efficiency 0.72) pulls about 4,500 lb; on sand (0.50) only 3,125 lb, because slip wastes power. Answers 'how much can it pull' instead of the power from a measured pull. Traction can limit the usable pull below this; ballast and tires govern.

pull_lb = 375 × drawbar_hp / speed_mph; a PTO rating converts first with drawbar_hp = pto_hp × tractive_efficiency. The inverse of drawbar_hp = (pull × speed) / 375.

ASABE D497 (Agricultural Machinery Management Data) by name; Nebraska Tractor Test Lab publications.

Nebraska Tractor Test data free at tractortestlab.unl.edu.

Estimate. AHJ and licensed professional govern.

Field names used by the API: power_hp, power_basis, speed_mph, surface, pull_lb

Tractive efficiency concrete 0.87 / firm soil 0.72 / tilled 0.55 / sand 0.50; a soft surface wastes power as slipASABE D497
Traction may limit the power-based pull can exceed the traction limit (weight x soil coefficient); ballast and tires govern the usable pulltraction mechanics