Acres per Hour Calculator (field capacity of farm machines, ha/h)

Understanding the field capacity (acres per hour) calculator — concept and principle

Field capacity is the area a tractor, sprayer, planter or combine covers per hour. This calculator finds the theoretical and effective capacity from working width, speed and field efficiency, and estimates how long a field will take.

Turning, overlaps and refills cut the 4.8 ha/h theoretical rate to 3.84 ha/h, so 40 ha takes about 10 h 25 min.

How it is calculated

Theoretical capacity (metric) = width (m) × speed (km/h) ÷ 10, in ha/h, because 1 km × 1 m = 1,000 m² and 1 ha = 10,000 m².
Theoretical capacity (US) = width (ft) × speed (mph) ÷ 8.25, in acres/h, because 43,560 ft² ÷ 5,280 ft = 8.25.
Effective capacity = theoretical × field efficiency.
Field time = field size ÷ effective capacity; 1 acre = 0.40469 ha.

The principle

A machine sweeps a strip as wide as its working width at its forward speed, so area per hour is width × speed. In practice it does not work every minute: it turns at headlands, overlaps passes, stops to refill seed, spray or fertilizer, and unloads grain. Field efficiency captures the share of time actually spent working. Typical efficiencies depend on the operation, field shape and size, and logistics.

Worked example

Default inputs: metric, width 6 m, speed 8 km/h, efficiency 80%, field 40 ha.

Theoretical capacity = 6 × 8 ÷ 10 = 4.8 ha/h.
Effective capacity = 4.8 × 0.80 = 3.84 ha/h, or 3.84 ÷ 0.40469 ≈ 9.49 acres/h.
Time for 40 ha = 40 ÷ 3.84 ≈ 10.42 h = 10 h 25 min.
Area in an 8-hour day = 3.84 × 8 ≈ 30.7 ha, about 75.9 acres.

Each point is the calculator re-run with only “Effective working width” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Effective working width	Effective field capacity (ha/h)
1.5	0.96
3	1.92
4.5	2.88
6	3.84
7.5	4.8
9	5.76
12	7.68

How to read the result

Use the effective capacity to plan workdays, compare machines or decide whether a wider implement is worth buying. Raising efficiency (larger, regular fields; fewer refill stops) can save as much time as a faster speed. Weather windows matter: planting and harvest often have only a few suitable days.

Common mistakes

Using the implement's overall width instead of its effective working width (accounting for overlap).
Assuming 100% efficiency.
Using road speed instead of average field speed.
Mixing hectares and acres.

Keep in mind: Efficiency varies with field conditions, operator and machine. Use the result for planning, and follow machinery safety guidance.

Frequently asked questions

How do I calculate acres per hour?

Width (ft) × speed (mph) ÷ 8.25 × field efficiency.

What is a typical field efficiency?

It varies by operation; published engineering data give typical ranges for each type of machine.

Why is the constant 8.25?

One acre is 43,560 ft² and one mile is 5,280 ft; 43,560 ÷ 5,280 = 8.25.

Sources: ASABE Standard D497, Agricultural Machinery Management Data · ASABE Standard EP496, Agricultural Machinery Management

Checked 9 Nov 2026. Hanna M., “Estimating the Field Capacity of Farm Machines”, Iowa State University Extension and Outreach, PM 696 (Ag Decision Maker A3-24), revised May 2016: effective field capacity (acres/h) = width (ft) × speed (mph) × field efficiency (%) ÷ (8.25 × 100); Table 1 typical field efficiencies.

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