Acres Per Hour Calculator: Field Capacity, Formula & Mowing Time
If you work the land you care about one number more than most—how much ground you can cover in an hour. This Acres Per Hour Calculator turns your tool’s width and travel speed into a clean capacity estimate, then shows how long that same setup will take to finish a plot. It also accounts for real-world overlap between passes, so your plan matches the day you have on the ground.
What “acres per hour” really means
Acres per hour (ac/hr) is your field capacity—the area you can cover in one hour at a given working speed and effective tool width. In a perfect world the number would be simple width × speed with zero waste. Real fields are not billiard tables. You turn, you overlap a bit, you slow down on rough patches, and you stop to empty a bagger or lift the implement. That is why solid planning distinguishes between:
- Theoretical Field Capacity (TFC): the best-case area rate if you drove nonstop in perfectly straight adjacent passes.
- Effective Field Capacity (EFC): the realistic rate after losses to overlap, turns, adjustments, and other delays.
Most jobs live somewhere between those two. Your calculator defaults to a modest overlap percentage to keep estimates honest.
Field capacity formulas (imperial & metric)
Two classic ways to compute capacity exist. Pick the one that matches your units then convert if needed.
Imperial shortcut (ac/hr)
Effective Field Capacity (ac/hr) =(Speed in mph × Effective width in ft × Field efficiency) ÷ 8.25
The 8.25 constant converts mph·ft to acres per hour. This presentation of the formula is widely used in agricultural engineering texts and extension publications. See references below for details.
Metric shortcut (ha/hr)
Effective Field Capacity (ha/hr) =(Speed in km/h × Effective width in m × Field efficiency) ÷ 10
Dividing by 10 handles the km→m and ha conversion in one step: 1 ha = 10,000 m².
What counts as “effective width”?
When you slightly overlap each pass, the cutting or working width that truly counts is smaller than the tool’s full width. The calculator treats that with a simple reduction:
Effective width = Physical width × (1 − overlap%)
For example, a 60-inch deck with 10% overlap works like a 54-inch deck. That one line keeps your plan realistic without asking you to guess a separate “field efficiency” factor for overlap.
Worked example you can copy
Let’s run one scenario twice—once in metric and once in imperial—to show the math behind the button.
Scenario
- Deck width: 1.5 m (about 59 in)
- Overlap: 10%
- Travel speed: 6 km/h
Metric path
- Effective width = 1.5 m × (1 − 0.10) = 1.35 m.
- EFC (ha/hr) = (6 × 1.35) ÷ 10 = 0.81 ha/hr.
- Convert to acres per hour: 0.81 ha/hr × 2.471 = 2.00 ac/hr (rounded).
Imperial path
- Width: 60 in = 5 ft. Effective width with 10% overlap → 4.5 ft.
- Speed: 3.7 mph (≈ 6 km/h).
- EFC (ac/hr) = (3.7 × 4.5 × 1.00) ÷ 8.25 = 2.02 ac/hr (matches our metric result).
You can check this against your own conditions by editing the width, speed, and overlap in the calculator. The result will update instantly and the number will land in the same ballpark as a stopwatch and GPS would on the ground.
From capacity to mowing time
Once you know acres per hour you can flip the math to predict job time. It is just area divided by rate:
Time (hours) = Plot area ÷ EFC
If you prefer hours and minutes, the calculator breaks it out for you. Here is a quick case:
- Capacity: 2.0 ac/hr
- Plot size: 5 acres
- Time = 5 ÷ 2.0 = 2.5 hours → 2 hours 30 minutes
That is planning gold when you need to schedule fuel, labor, or daylight.
Units & conversions at a glance
Use any of the unit pairs below. The calculator converts silently so you can work in what feels natural.
| Quantity | Metric | Imperial / US | Handy conversion |
|---|---|---|---|
| Width | meters (m), centimeters (cm) | feet (ft), inches (in) | 1 m = 3.2808 ft, 1 in = 0.0254 m |
| Speed | km/h, m/s | mph, ft/s | 1 mph = 1.609 km/h, 1 m/s = 3.6 km/h |
| Area rate | ha/hr, m²/s | ac/hr, ft²/s | 1 ha = 2.471 ac, 1 ac = 4046.856 m² |
If you work mainly in miles per hour and feet, the 8.25 constant keeps your math fast. Multiply mph by feet of effective width, then divide by 8.25. That’s it.
Overlap, field efficiency & why plans drift
Overlap matters because it turns “paper width” into “real width.” A little overlap prevents skips and assures a perfectly covered finish, yet it reduces capacity. Guidance tools cut overlap, a sharp blade tracks straighter, and well-planned headlands reduce time lost at ends.
Extension guides describe capacity losses to overlap, turning, and adjustments under the umbrella of field efficiency. The famous imperial formula uses that efficiency directly along with speed and width, then divides by 8.25 to land on acres per hour. The metric form divides by 10 and works the same idea. See the sources below for clear, plain-language explanations from university and extension authors.
What overlap should I assume?
- 10% overlap is a realistic default for many mowing and seeding jobs.
- 5% overlap is possible with guidance or careful line keeping.
- 15–20% overlap may happen on irregular fields or when fatigue sets in.
If you know your own pattern, set the overlap percentage and the calculator adjusts the effective width for you. You do not need to estimate a separate efficiency number just for overlap.
Ways to improve acres per hour
Small changes stack up. Try these ideas the next time you head out.
- Reduce overlap deliberately. Use a lightbar or simple reference points. A two-inch improvement on each pass adds up quickly over dozens of strips.
- Plan headlands first. Make one or two passes around the edges to create turn space. You turn smoothly and maintain speed through the middle lanes.
- Match gear and throttle to the job. “Gear up, throttle down” (within manufacturer guidance) helps you carry steady speed without wasted fuel.
- Keep the deck sharp and level. A sharp blade tracks cleaner. You drift less. Your overlap shrinks naturally.
- Check ballast and tire pressure for traction. Proper setup limits slip in loose ground, which protects speed and straightness.
- Use guidance where it pays. Even a basic GPS line helps at dusk or on long runs where eyes get tired.
Typical tool widths and practical speeds
These ranges are not rules. They simply reflect what many operators use for reliable work quality. Your ground and machine will tell you where to land.
| Task / implement | Common working width | Typical speed | Notes |
|---|---|---|---|
| Lawn / pasture mowing (riding) | 42–72 in (1.1–1.8 m) | 3–6 mph (4.8–9.7 km/h) | Choose speed the turf can handle without scalping; bagging slows you down. |
| Brush mowing (rotary cutter) | 4–7 ft (1.2–2.1 m) | 2–5 mph (3–8 km/h) | Heavy material demands steady but slower travel. |
| Seeder / drill (small acreage) | 4–10 ft (1.2–3.0 m) | 4–7 mph (6–11 km/h) | Seed rate accuracy sets your top speed. |
Use the table as a starting point then dial the numbers for your machine, terrain, and quality target. The calculator handles the math while you tune overlap and speed.
Frequently asked questions
What is the difference between hectares per hour and acres per hour?
They are the same idea in different units. One hectare equals 2.471 acres. Multiply ha/hr by 2.471 to get ac/hr. Divide ac/hr by 2.471 to return to ha/hr.
Why do some references include “field efficiency” in the formula?
Many textbooks use field efficiency to lump all time and distance losses—turning, overlap, refilling, adjustments—into one factor between 0 and 1. Our approach folds overlap into effective width and leaves the rest at 100% by default, which keeps the inputs simple. If you want to reflect additional delays you can mentally multiply the answer by your estimated efficiency (for example 0.85).
Does a faster speed always save time?
Not always. Beyond a sensible limit you bounce more, you wander more, and your overlap creeps up. That extra overlap erases the time you thought you gained, and surface quality can suffer. Find the highest speed that keeps your passes straight and safe.
What if the plot has many trees or islands?
Irregular fields reduce effective capacity. You spend more time turning and lining up. Estimate overlap on the higher side and assume a modest efficiency haircut when the layout is tight.
How accurate is the “time to complete” result?
It is as accurate as the inputs. If you measure width at the blades, pick a realistic travel speed, and set overlap honestly, the time estimate will stay close. Weather, slope, bagging, and obstacles can still stretch a job.
Further reading
Clear references keep planning honest. These resources explain the standard field capacity formulas and the practical factors that nudge real jobs off the ideal line.
- University of Florida IFAS, Farm Management, discusses field capacity concepts and the balance between theoretical and effective output.
See section on capacity. - Iowa State University Ag Decision Maker—discussion of machine capacity and costs, including field capacity and field efficiency framing.
A3-25 Machinery costs. - Research on overlaps and path efficiency in field operations: Kharel et al., 2020, “Tractor path overlap…,” shows how overlaps reduce efficiency and why guidance matters.
Read the paper. - Team Forage (UW Extension), tips that cut overlapping passes and save fuel/time.
Practical strategies.
How to use the calculator like a pro
- Enter tool width and pick a unit. If you work with inches, no problem—select in, and the tool converts behind the scenes.
- Enter your steady working speed. Use the speed you can hold for a complete pass, not the peak on a long downhill stretch.
- Check the overlap setting. Ten percent keeps results honest. If you run with guidance you can nudge it lower.
- Review the rate card. You’ll see the number in your preferred area and time units—ac/hr, ha/hr, and their companions.
- Switch to “Mowing time.” Type the plot size to get hours and minutes for the job. The time uses the rate you just calculated.
Why this calculator feels different
- Friendly defaults, honest math. The overlap control is explicit so you can see how much it matters.
- Results in a dedicated card. Big, readable numbers in your chosen units with a one-tap copy.
- Metric–imperial without friction. Flip units anywhere. The formulas update silently.
Troubleshooting quick hits
- Nothing happens? Check that width and speed are both numbers greater than zero.
- Results seem too low? Reduce overlap, confirm you didn’t mix inches and feet, and verify that the speed is working speed rather than transport speed.
- Time estimate too optimistic? Add a small buffer for breaks, bagging, or refueling. No calculator sees rainclouds and stuck gates.
Cheat sheet: constants behind the curtain
1 acre = 43,560 ft²1 mile = 5280 ftmph × ft ÷ 8.25 → ac/hr(the “8.25” roll-up constant)km/h × m ÷ 10 → ha/hr1 ha = 2.471 ac
Copy-worthy examples
Use these ready-reckoners when you need a fast plan.
| Deck width | Speed | Overlap | Capacity (approx.) |
|---|---|---|---|
| 48 in (4.0 ft) | 4.5 mph | 10% | ≈ (4.5 × 3.6) ÷ 8.25 = 1.96 ac/hr |
| 60 in (5.0 ft) | 5.5 mph | 10% | ≈ (5.5 × 4.5) ÷ 8.25 = 3.00 ac/hr |
| 72 in (6.0 ft) | 5.0 mph | 15% | ≈ (5.0 × 5.1) ÷ 8.25 = 3.09 ac/hr |
Design notes for accuracy nerds
The calculator uses effective width to handle overlap, then applies the standard field capacity relations noted in extension literature. If you prefer the efficiency-driven form, set an additional “efficiency factor” in your head and multiply the result. For example, a 2.5 ac/hr rate at 85% overall efficiency becomes 2.13 ac/hr.
Safety and machine care matter more than a number
Big rates look impressive. Quality and safety build a business. Stay within the manufacturer’s recommendations for deck height, PTO speed, and transport limits. Slow for slopes and wet ground. Sharp blades and a level deck make cleaner cuts and reduce overlap pressure. You deliver better work and protect both customer trust and equipment.
You now have everything you need to plan a day’s work with confidence. Set your width and speed, be honest about overlap, then let the calculator do the heavy lifting while you focus on the field.
