Field Capacity Calculator: Acres per Hour

This calculator works out the field capacity of a tractor implement, sprayer or combine. Enter the working width, the ground speed and a field efficiency for turns, filling and overlap; you get acres per hour and hectares per hour.

Formula

Acres per hour = width (ft) × speed (mph) × efficiency ÷ 100 ÷ 8.25. The 8.25 comes from 43,560 ft² per acre ÷ 5,280 ft per mile.

Worked Example

A 30 ft implement at 6 mph with 80% field efficiency.

1. Theoretical = 30 × 6 ÷ 8.25 = 21.82 acres/h
2. Effective = 21.82 × 0.80 = 17.45 acres/h
3. In hectares: 17.45 × 0.4047 = 7.06 ha/h

How to read the result

Divide the field size by the result to plan the hours. Typical efficiencies are around 70-90% for tillage and planting and lower for small or irregular fields.

Limits and common mistakes

• Use the effective width actually covered, after overlap.
• Speed must be the real ground speed in the field.

Frequently Asked Questions

Where does 8.25 come from?

43,560 ÷ 5,280 = 8.25.

How many acres per hour with a 20 ft disc at 5 mph?

About 9.7 acres/h at 80% efficiency.

What is field efficiency?

The share of time spent actually working, after turns, filling and stops.

Does this work for sprayers?

Yes, with the boom width as the working width.

in w | Working width | ft | 30 | 0 | 200
in v | Ground speed | mph | 6 | 0 | 40
in eff | Field efficiency | % | 80 | 1 | 100
out ac | Field capacity | acres/h | w * v * eff / 100 / 8.25 | 2
out ha | Field capacity | ha/h | ac * 0.40468564224 | 2