Acres per hour calculator
Enter your working width and speed in metric or imperial. Field efficiency is what turns theory into reality.
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How do you calculate acres per hour?
Multiply the working width in feet by the ground speed in miles per hour and divide by 8.25. That gives theoretical capacity, which you then multiply by field efficiency — typically 70% to 85% for tillage and seeding — to get the acres you will actually cover.
Where 8.25 comes from
The constant looks arbitrary and is not. An acre is 43,560 square feet, and a mile is 5,280 feet. Working a strip one foot wide for one mile covers 5,280 square feet, so 43,560 divided by 5,280 gives 8.25.
That means the formula is really width times speed divided by that conversion, and the 8.25 is doing nothing more mysterious than turning feet-miles into acres.
Because the constant is imperial, the metric route runs through a conversion. This calculator does that conversion for you and reports both acres and hectares, since Canadian farms routinely use both.
Field efficiency is the honest part
Theoretical capacity assumes the implement is working at full width and full speed every second it is in the field. Nothing does.
Turning at headlands, overlapping passes, refilling seed or spray, adjusting, and stopping for blockages all cost time. Field efficiency is the fraction of the theoretical figure you actually achieve, and it is where most planning estimates go wrong.
Small or irregular fields punish efficiency hardest, because headland turns are a larger share of the total. A 30-metre drill in a small awkward field can lose more to turning than a 12-metre one in a large square one.
The formula
Theoretical capacity first, then scaled by efficiency.
theoretical acres/hr = width (ft) × speed (mph) ÷ 8.25effective acres/hr = theoretical × field efficiencyhectares/hr = acres/hr × 0.4047typical field efficiency:tillage and seeding 70% – 85%spraying 65% – 80%combining 65% – 80%mowing 75% – 85%
Working width is the width actually covered, not the width of the machine. A 12-metre drill run with a half-metre overlap is covering 11.5 metres, and using 12 in the formula overstates your capacity by more than 4%.
Guidance systems earn much of their return here, by cutting that overlap to near zero and lifting effective width back toward the machine width.
Worked example: a 12 metre drill at 10 km/h
A 12 metre seed drill working at 10 km/h with 80% field efficiency.
- Width in feet39.37 ft
- Speed in mph6.214 mph
- Theoretical = 39.37 × 6.214 ÷ 8.2529.65 acres/hr
- At 80% efficiency23.72 acres/hr
- In hectares9.60 ha/hr
About 23.7 acres or 9.6 hectares an hour, so a 500 acre field takes roughly 21 hours.
At 100% efficiency the same setup would suggest under 17 hours for that field. The four-hour difference is entirely headland turns, refills and overlap — which is exactly why the efficiency figure belongs in the calculation rather than being applied as a mental fudge afterwards.
Improving the number
- Guidance and section control cut overlap, raising effective width
- Larger, squarer fields reduce the proportion of time spent turning
- Faster refilling — bigger tanks, tender trucks — lifts efficiency directly
- Higher speed helps only until ride quality or work quality suffers
- Reducing headland turns by running longer passes has an outsized effect on small fields
Common questions
What is the acres per hour formula?
Width in feet times speed in miles per hour, divided by 8.25. That gives theoretical capacity. Multiply by your field efficiency, usually between 0.65 and 0.85, to get what you will actually achieve.
Why 8.25?
It converts feet-miles into acres. An acre is 43,560 square feet and a mile is 5,280 feet, and 43,560 divided by 5,280 is 8.25. The constant is doing a unit conversion, nothing more.
What is a realistic field efficiency?
Between 70% and 85% for tillage and seeding, 65% to 80% for spraying and combining, and 75% to 85% for mowing. Small or irregular fields sit at the bottom of those ranges or below, because headland turns take a larger share of the time.
Should I use machine width or working width?
Working width — the width you actually cover after overlap. A 12 metre drill run with half a metre of overlap covers 11.5 metres, and using the machine width overstates capacity by over 4%.
Where these numbers come from
- Government of Saskatchewan — Machinery costing and field capacity Provincial machinery costing guides using the standard field capacity formula.
Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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