Acres Per Hour Calculator
Enter implement width, ground speed and field efficiency to get your true work rate — acres per hour, hectares per hour, and minutes per acre — with every step of the math shown. Built for spraying, mowing, tilling, planting and harvesting.
🔒 100% client-side — your numbers never leave this page.
Show your work
Start from the rate you need and solve for the speed or width that gets you there.
Show your work
How long will the job take? Uses your work rate from the first tab (or enter one manually).
Typical speeds & efficiencies by job
Planning ranges gathered from extension guidance and operator reports. Tap Use to load a row into the calculator, then adjust for your field.
| Operation | Typical speed | Typical efficiency |
|---|
Quick unit converter
The same conversions the calculator uses internally.
Acres ⇄ hectares
Feet ⇄ metres (width)
mph ⇄ km/h (speed)
Inches → feet (mower decks)
Worked examples
Real scenarios, verified against the formula. Tap Load to replay one in the calculator.
1 · Spraying a quarter section
60 ft boom, 8 mph, 85% efficiency (refill stops on a big square field).
2 · Bush-hogging pasture
5 ft rotary cutter, 3 mph, 85% efficiency — the classic forum example.
3 · Hitting a 20 ac/h target
Reverse: what speed does a 40 ft implement need at 80% efficiency?
Methodology
The exact math this page uses, where every number comes from, and the honest limits.
The formula
Why 8.25? It is exact, not empirical. One mile is 5,280 feet, so a machine moving at 1 mph covers a strip 5,280 feet long each hour. Multiply by the width in feet and you have square feet per hour. One acre is 43,560 square feet, and 43,560 ÷ 5,280 = 8.25. So width × speed ÷ 8.25 converts directly to acres per hour. (Iowa State Extension PM 696 derives it identically.)
Theoretical vs effective field capacity
Theoretical field capacity = width × speed ÷ 8.25 — the ceiling at 100% efficiency: full width, no turns, no stops. Effective field capacity multiplies that by field efficiency to reflect reality: headland turns, overlap between passes, refilling seed/chemical tanks, unloading grain, and obstacles. This calculator shows both, so the cost of inefficiency is visible.
Choosing field efficiency
Efficiency is the only judgment call in the formula. Use your own measured records when you have them. Otherwise: 90% — large square fields with GPS auto-steer; 80% — good conditions, moderate turns; 70% — average or irregular fields; 60% — small, obstacle-filled, or frequently-refilled work. These bands align with ASABE machinery-management data commonly cited by extension services.
Metric version
Hectares/hour = width (m) × speed (km/h) × efficiency ÷ 10, because 10,000 m² per hectare ÷ 1,000 m per km = 10. One acre = 0.404686 ha.
Honest limits
This is a planning estimate, not a guarantee. It does not model soil conditions, slope, crop density, operator skill, weather windows, or breakdowns. Measure a real timed pass (see FAQ: the 88-foot method) and calibrate efficiency to your farm.
What this tool is (and isn't)
- Is: a work-rate calculator — how fast an implement covers ground (acres/hour, hectares/hour).
- Isn't an area converter — for acres ↔ hectares ↔ square feet alone, use a unit converter.
- Isn't a speed converter — for mph ↔ km/h alone, use a speed converter.
- Isn't a cost estimator — custom farming rates ($/acre) need fuel, labor and depreciation inputs this tool deliberately excludes.
- Isn't a spray calibration tool — GPA, nozzle flow and pressure need a dedicated sprayer calibration calculator.
Frequently asked questions
Straight answers, same math as the calculator above.