Acres Per Hour Calculator
Work out how many acres per hour a tractor and implement really cover, and how long a field of a given size will take.
🌱 What is Acres Per Hour?
Acres per hour is the field work rate of a tractor and implement combination, in other words how much ground the machine finishes in one hour of in-field time. Agricultural engineers call it field capacity, and they split it into two numbers. Theoretical field capacity assumes the implement works at its full rated width, at a constant speed, and never stops. Effective field capacity multiplies that ideal by a field efficiency factor, which absorbs everything the ideal ignores: headland turns, overlap between adjacent passes, refilling a seed hopper or spray tank, unloading grain, and the short pauses to adjust a setting or clear a blockage.
The number drives a surprising amount of practical decision making. A grain farmer sizing a new combine works backwards from the acres that must come off in a typical harvest window, then divides by the hours per day and the weather-safe days available to find the rate the machine has to hit. A custom operator quoting a spraying job needs the rate to convert an hourly cost into a per acre price that still leaves a margin on a small, awkward field. A contractor planning a week of mowing uses it to decide whether three sites fit into one day or need two. Even a smallholder deciding between a 6 ft and an 8 ft topper is really comparing acres per hour against purchase price.
The most common mistake is to treat the rated width of the implement as the working width. If you habitually overlap by a foot on a 30 ft header, your true working width is 29 ft and you have quietly given away three percent of your capacity on every pass, every day. The second most common mistake is optimism about efficiency. Very few operations sustain 90 percent. Long rectangular fields with wide implements and on-the-move unloading might reach 85, while small irregular paddocks with frequent refills routinely fall below 60. A third trap is counting road travel between fields inside the field time, which makes the calculated efficiency look far worse than the machine deserves.
This calculator does the conversion in both unit systems, shows the theoretical rate next to the effective rate so the cost of turning and overlap is visible as a number, and reports the hours and minutes needed to finish a field of the size you enter. The chart plots finish time against ground speed, which makes the diminishing return on speed obvious, and the comparison table lets you scan several speeds at once before you decide how hard to push.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Combine Harvesting a Quarter Section
30 ft header, 5 mph, 80% efficiency, 160 acre field
Example 2 — Contract Mowing a Small Site
12 ft flail mower, 4 mph, 85% efficiency, 40 acre parkland
Example 3 — Self-Propelled Sprayer on a Large Block
60 ft boom, 12 mph, 65% efficiency, 500 acre block
Example 4 — Metric Seed Drill
6 m drill, 8 km/h, 75% efficiency, 20 hectare field
❓ Frequently Asked Questions
🔗 Related Calculators
What is the formula for acres per hour?
Acres per hour = working width in feet times ground speed in mph times field efficiency, all divided by 8.25. The 8.25 comes from 43,560 square feet in an acre divided by 5,280 feet travelled per hour at one mph. A 30 ft implement at 5 mph and 80 percent efficiency covers 14.55 acres per hour.
Where does the number 8.25 come from?
One mile per hour moves the machine 5,280 feet in an hour, so one foot of width sweeps 5,280 square feet per hour. An acre is 43,560 square feet, and 43,560 divided by 5,280 is 8.25. Dividing width times speed by 8.25 therefore converts feet and mph straight into acres per hour.
What is field efficiency?
Field efficiency is the share of clock time the implement spends actually working at full width. It absorbs headland turns, overlap between passes, filling and unloading stops, and short adjustments. Typical values run 60 to 70 percent for planters, 70 to 85 percent for tillage and 65 to 80 percent for combines.
What is the difference between theoretical and effective field capacity?
Theoretical field capacity assumes the implement works at full rated width, at constant speed, with no stops. Effective field capacity multiplies that by field efficiency, so it reflects the acres you actually finish. The gap is often a quarter of the working day.
How do I calculate hectares per hour instead?
Use hectares per hour = width in metres times speed in km/h times efficiency divided by 10. A 6 m drill at 8 km/h and 75 percent efficiency covers 3.6 ha per hour. Switch the calculator to metric mode and it converts your existing figures for you.
How long will it take to cover my field?
Divide the field size by the effective rate. A 160 acre field at 14.55 acres per hour takes 11.0 hours of in-field time. Remember that this excludes road travel between fields, so a working day rarely delivers the full figure.
What is a typical field efficiency for a combine harvester?
Most combines run between 65 and 80 percent. Grain tank unloading on the move keeps the number high, while frequent stops to unload into a stationary trailer, lodged crop or wet patches will push it to 60 percent or below.
Does increasing speed always increase acres per hour?
Mathematically yes, but only up to the point where quality collapses. Planters lose seed spacing accuracy above about 6 mph unless fitted with high speed meters, sprayers lose coverage as boom bounce grows, and combines start losing grain over the sieves. Past that point the extra acres cost more than they earn.
Should I use the full implement width in the calculation?
Use the effective working width, which is the rated width minus your habitual overlap. Guidance systems cut overlap to a few centimetres, while eyeballed passes commonly overlap 5 to 10 percent, and that overlap is a direct loss of capacity.
How do I turn acres per hour into a custom rate per acre?
Divide your total hourly cost, which includes fuel, repairs, depreciation and labour, by the effective acres per hour. If the machine costs 180 per hour to run and covers 14.55 acres per hour, the break-even charge is about 12.37 per acre before profit.
Why is my real work rate lower than the calculator says?
The usual causes are an optimistic efficiency figure, forgetting overlap when entering width, and counting road travel or lunch inside the field time. Time one full field with a stopwatch, then back-calculate your own efficiency and reuse that number.
Can I use this for mowing, spraying or snow clearing?
Yes. The geometry is identical for any machine that sweeps a fixed width across ground at a steady speed, so it works for lawn mowing contractors, boom sprayers, roadside flails and even snow ploughs. Only the sensible efficiency value changes.