Acres Per Hour Calculator: Field Coverage Rate and Time to Complete
Enter your implement width, travel speed, and field efficiency to get your coverage rate in acres per hour and hectares per hour. Add an optional field area and the calculator shows exactly how long the job will take. The "Show your work" panel walks through the arithmetic step by step with your real numbers.
Formula
Worked example
A disc harrow with a 15 ft working width at 6 mph with 80% efficiency and 10% overlap: effective width = 15 ft x 0.90 = 13.5 ft; acres per hour = (13.5 x 6 x 0.80) / 8.25 = 64.8 / 8.25 = 7.85 ac/hr. A 200-acre field takes 200 / 7.85 = 25.5 hours.
The acres per hour formula explained
The standard agronomy formula for field coverage rate is:
Acres per hour = (Width in feet x Speed in mph x Efficiency) / 8.25
The constant 8.25 comes from the definition of an acre: 43,560 square feet divided by 5,280 feet per mile equals 8.25. Multiply width (ft) by speed (mph) and you get square feet per hour, then divide by 43,560/5,280 to convert to acres. The efficiency factor (expressed as a decimal between 0 and 1) accounts for the time lost to turns, stops, refuelling, and any passes that do not cover new ground.
If you prefer metric inputs, convert first: 1 metre = 3.28084 feet, 1 km/h = 0.621371 mph. The output in acres per hour multiplied by 0.404686 gives hectares per hour.
Field efficiency: what it is and how to choose a value
Field efficiency is the single biggest variable in the formula. It represents the fraction of time your implement is actively covering new ground. The ASABE (American Society of Agricultural and Biological Engineers) publishes standard efficiency ranges by equipment type:
- 90% (Excellent): Large, square or rectangular fields with GPS auto-steer. Very few stops, long straight passes.
- 80% (Good): Typical well-managed farms. Moderate turns, occasional stops for obstacles or end-rows.
- 70% (Average): Smaller fields, irregular shapes, more frequent headland passes, or manually steered equipment.
- 60% (Poor): Very small or oddly-shaped fields, frequent refilling, or fields with many obstacles.
When in doubt, use 70-75% for planning. It is better to budget slightly more time and finish early than to under-estimate and miss a planting window.
How overlap affects your coverage rate
Overlap is the intentional extra width covered on each pass to prevent missed strips. A 10% overlap means your effective swath is 10% narrower than your nominal implement width, which directly reduces your acres per hour by the same proportion. This calculator subtracts overlap before applying the formula so your coverage estimate is realistic.
GPS-guided auto-steer systems typically reduce overlap to 2-5%, recovering most of the lost productivity. On a 30-ft sprayer at 12 mph, reducing overlap from 10% to 3% adds roughly 15% to your coverage rate, which can mean finishing a large field a full hour sooner.
Using this calculator for job costing and scheduling
Enter your field area in the optional field and the calculator converts your coverage rate into hours-to-complete. You can use that figure to:
- Build a realistic daily schedule across multiple fields
- Price custom fieldwork by the hour or acre (hours x your hourly rate)
- Decide whether a second pass (e.g., cross-cultivation) fits in the weather window
- Compare different implement widths or speed settings before purchasing or changing practice
Remember that the formula assumes constant speed and a single field at a time. Add buffer time for travel between fields, fuelling, and any unexpected delays.
Limitations and when the formula over-estimates
The formula gives an average rate under the conditions you enter. It will over-estimate if:
- Your field has a complex shape with many short passes (each pass wastes a disproportionate share of time on turns)
- Soil conditions force you to slow down partway through (wet spots, steep slopes)
- The implement needs frequent cleaning or adjustment (e.g., planters in sticky soil)
- You are working around waterways, trees, or infrastructure that require hand-moves
For detailed project planning, break the field into sections and calculate each separately using the realistic speed and efficiency for that zone.
Typical acres per hour by equipment type
| Equipment | Typical width | Speed range | Typical ac/hr |
|---|---|---|---|
| Push mower | 2 ft | 2-3 mph | 0.3-0.6 |
| Riding mower | 4-6 ft | 4-6 mph | 1.5-3.5 |
| Zero-turn mower (residential) | 5-7 ft | 5-8 mph | 2.5-5 |
| Zero-turn mower (commercial) | 6-10 ft | 7-10 mph | 4-9 |
| Tractor + rotary cutter | 10-15 ft | 5-8 mph | 5-12 |
| Disc harrow | 12-20 ft | 5-7 mph | 6-14 |
| Field cultivator | 20-40 ft | 6-8 mph | 12-28 |
| Grain drill | 10-30 ft | 5-7 mph | 5-20 |
| Row-crop planter | 15-60 ft | 4-6 mph | 6-33 |
| Pull-type sprayer | 30-90 ft | 10-15 mph | 33-147 |
| Self-propelled sprayer | 60-132 ft | 12-20 mph | 80-300 |
Representative ranges under good field conditions (80% efficiency). Actual results depend on field size, terrain and operator skill.
Frequently asked questions
What is the formula for acres per hour?
Acres per hour = (Width in feet x Speed in mph x Field efficiency) / 8.25. The 8.25 factor converts square feet per hour to acres per hour (43,560 sq ft/acre divided by 5,280 ft/mile). Subtract your overlap percentage from the width first to get the effective working width.
How do I calculate acres per hour for a mower?
Measure your mower deck width in feet, note your average cutting speed in mph, and estimate field efficiency (70-80% is typical for most lawns and pastures). Plug those three numbers into the formula above. A 6 ft deck at 5 mph with 75% efficiency covers (6 x 5 x 0.75) / 8.25 = 2.73 acres per hour.
What field efficiency should I use?
Use 80% for most well-managed farm fields. Drop to 70% for smaller or irregular fields, and to 60% if there are frequent stops and many obstacles. Only use 90% for very large, rectangular fields with GPS auto-steer. When in doubt, 70-75% keeps your estimates conservative and avoids scheduling surprises.
Why divide by 8.25 in the acres per hour formula?
One acre equals 43,560 square feet, and one mile equals 5,280 feet. Dividing 43,560 by 5,280 gives 8.25. So when you multiply width (ft) by speed (mph), you get square feet per hour; dividing by 8.25 converts that area to acres per hour. It is a fixed unit-conversion constant, not an estimate.
How many acres per hour can a tractor cover?
It depends on implement width and speed. A tractor pulling a 20 ft disc at 6 mph with 80% efficiency covers about (20 x 6 x 0.80) / 8.25 = 11.6 ac/hr. Wider implements and higher speeds multiply quickly: a 40 ft field cultivator at 7 mph (80% efficiency) reaches (40 x 7 x 0.80) / 8.25 = 27.2 ac/hr.
How do I convert acres per hour to hectares per hour?
Multiply acres per hour by 0.404686. For example, 10 ac/hr = 10 x 0.404686 = 4.05 ha/hr. This calculator shows both units simultaneously so you do not need to convert manually.
How long does it take to mow 100 acres?
Divide the field area by your coverage rate. At 5 ac/hr (a typical riding mower), 100 acres takes 100 / 5 = 20 hours. At 30 ac/hr (a large commercial mower or tractor-mounted cutter), the same field takes under 3.5 hours. Enter your field area in the optional field above to get a precise estimate.