How Many Acres per Hour Can You Mow or Till? The Field Capacity Formula Explained

Do the theoretical maths on a 5-foot brush mower at 5 mph and you get about 3 acres an hour. Operators who mow for a living report something closer to 1 acre an hour with the same machine. The gap is not bad driving; it is turns, overlaps, obstacles, slowing for rough ground and stops. Understanding that gap is what makes an acres per hour estimate useful for quoting a job or planning a weekend.

This guide explains the formula, the efficiency factor that most estimates ignore and how to estimate your own work rate. To run the numbers, use our acres per hour calculator.

The acres per hour formula

Agricultural engineers call this effective field capacity:

Acres per hour = width (ft) × speed (mph) × field efficiency ÷ 8.25

Hectares per hour = width (m) × speed (km/h) × field efficiency ÷ 10

The 8.25 constant converts units: a 1-foot strip driven for an hour at 1 mph covers 5,280 square feet, and 43,560 ÷ 5,280 = 8.25.

Worked example

A 10-foot mower at 5 mph and 80% efficiency covers 10 × 5 × 0.8 ÷ 8.25 = 4.85 acres per hour. At 100% efficiency it would be 6.06, the theoretical figure that never happens in practice.

Field efficiency is where estimates go wrong

Field efficiency is the share of time the machine is actually working at its full width. It drops with every turn, overlap, refill and stop. Typical planning ranges used in agricultural engineering are roughly:

Operation	Typical field efficiency
Mowing, open ground	75 – 85%
Tillage (disc, cultivator)	75 – 90%
Planting and seeding	60 – 75% (refilling seed)
Spraying	55 – 70% (refilling tanks)
Baling	65 – 80%

Small, irregular or obstacle-filled areas can fall well below these figures, which is why the real-world brush-hog rate of about an acre an hour is so far below theory.

Effective width is less than the machine width

You overlap passes to avoid leaving strips, so the effective cutting width is usually 6–12 inches less than the deck or implement width. On a 5-foot mower, using 4–4.5 feet in the formula gives more realistic answers. The same applies to sprayer booms and seeders.

Speed is limited by the ground, not the tractor

Rough, wet or tall vegetation forces lower speeds. Brush mowing tall growth may happen at 2–3 mph, while finish mowing a lawn can run faster. Quality also drops at high speed: uneven cuts, missed seed and spray drift.

How to estimate a real job

1. Measure the area in acres or hectares, excluding buildings and ponds. Our garden area calculator handles odd shapes.
2. Use effective width, not the brochure width.
3. Pick a realistic speed for the ground conditions.
4. Choose an efficiency from the table, lower for small or awkward fields.
5. Add travel and setup time between fields, which the formula does not include.

Using acres per hour to price work

Custom operators often price per acre, not per hour. If your real rate is 1.5 acres an hour and your hourly cost (machine, fuel, labour, profit) is $90, your break-even is $60 per acre before travel. Measuring your own acres per hour on a few jobs is the most reliable way to set rates. For land clearing quotes, see the land clearing cost calculator.

Frequently asked questions

How many acres per hour can a 5 ft bush hog mow?

The formula gives about 2.4 acres per hour at 5 mph and 80% efficiency, but operators commonly report around 1–1.5 acres per hour in real brush, because speeds are lower and fields are rarely ideal.

How many acres can I mow in a day?

Multiply your real acres per hour by working hours, minus travel and breaks. At 1.5 acres per hour over 7 working hours, roughly 10 acres.

Why is my real rate lower than the calculator?

Usually because of a lower effective width (overlap), slower speed in rough ground, or more turning than assumed. Lower the efficiency until it matches your experience.

How do I convert hectares per hour to acres per hour?

Multiply hectares per hour by 2.471.

Formula: standard effective field capacity equation used in agricultural engineering. Real-world mowing rates from owner reports on TractorByNet. Efficiencies are planning ranges; measure your own.