Free farm tool
Combine Workrate Calculator
Header width, forward speed, and an honest efficiency figure - get hectares and tonnes per hour, and how often a trailer needs to be there.
Workrate
3.8 ha/hr
In acres
9.3 ac/hr
Grain harvested
34 t/hr
Fills a 14t trailer
every 25 min
9 m × 6 km/h ÷ 10 × 70% = 3.8 ha/hr - at 9 t/ha that's 34 t/hr into trailers.
The formula
Workrate (ha/hr) = width (m) × speed (km/h) ÷ 10 × efficiency. The ÷10 converts metre-kilometres into hectares. Spot rate - what the machine covers while it's actually cutting at speed - is the brochure number. Whole-field workrate is what matters for planning, and the difference between them is the efficiency figure: turns on the headland, waiting to unload, blockages, and moves between fields.
Why the tonnes figure matters more
The ha/hr number sizes the harvest; the t/hr number sizes the trailer fleet. A combine putting 34 tonnes an hour into trailers needs a 14-tonne trailer arriving roughly every 25 minutes - if the round trip to the store, including tipping and any queue at the pad, takes 50 minutes, you need three trailers to keep the header in the crop. That arithmetic, and what to do when it doesn't balance, is covered in our guide to trailer logistics at harvest.
Planning numbers, not promises
Use conservative inputs. Speed varies with crop density, straw condition, and slope; efficiency collapses in small fields; and a weather window shortens the day at both ends. If last season you cut 520 ha in 15 combine days, that's your real workrate - the calculator is for testing changes (a wider header, an extra trailer) against it. Weighed loads per field, recorded as you go, are what make that hindsight available; see how to track harvest.
Frequently asked questions
How do you calculate combine workrate?
Header width in metres times forward speed in km/h, divided by 10, gives the spot workrate in hectares per hour. Multiply by a field efficiency of 60–80% to allow for turns, unloading, and stoppages. A 9m header at 6 km/h at 70% efficiency covers about 3.8 ha/hr.
What is a realistic field efficiency?
Most combines run 60–80% of their theoretical spot rate over a whole field. Big, open, regular fields with unloading on the move sit at the top end; small awkward fields with gateways, wet patches, and a trailer that isn't there when the tank's full sit at the bottom.
How many tonnes per hour does a combine harvest?
Workrate in ha/hr times yield in t/ha. The 3.8 ha/hr example in a 9 t/ha wheat crop is about 34 t/hr - which fills a 14-tonne trailer roughly every 25 minutes, and that number is what decides how many trailers you need.
How many hectares can a combine cut in a day?
At 3.8 ha/hr, a 10-hour cutting day is around 38 ha (about 94 acres). Real days vary hugely: dew burning off late, moisture climbing in the evening, breakdowns, and catchy weather can halve it, which is why harvest planning works from realistic averages rather than brochure figures.
Weighing loads this harvest? Stop adding them up by hand.
Harvestt records every weighbridge load against crop, field, and shed - and does this arithmetic for you, live.
Try Harvestt