Calculators · Machinery

Field capacity, work time and tractor power calculator

How much ground a tractor and implement cover depends on working width, speed and field efficiency — the share of time spent actually working rather than turning, overlapping or filling. These calculators give hectares per hour, the time a field takes, fuel used per hectare, and the drawbar power an implement needs.

Effective field capacity

Multiplies implement width by working speed and field efficiency. Small or irregular fields have lower efficiency because more time is spent turning at the headlands.

Results
Field capacity—ha/hHectares covered per hour.
Field capacity—acres/hAcres covered per hour.

Formula
ha/h = width [m] × speed [km/h] × efficiency / 10

Time to work a field

Divides field area by effective field capacity to estimate the working hours a job needs. Travel to and from the field, and refilling time, should be added separately.

Results
Working time—hoursTime needed to cover the field.

Formula
hours = area / (width × speed × efficiency / 10)

Fuel per hectare

Divides the tractor’s hourly fuel use by the area covered per hour. It is the fairest way to compare implements, tractors or working speeds on fuel cost.

Results
Fuel per hectare—L/haLitres used for each hectare worked.
Fuel cost per hectare—per haFuel cost of each hectare worked.

Formula
L/ha = fuel [L/h] / capacity [ha/h]

Drawbar power for an implement

Multiplies the implement’s draught force by working speed to give the power needed at the drawbar. Engine power must be considerably higher — typically 1.5 times or more — because of wheel slip and transmission losses.

Results
Drawbar power—Power delivered at the hitch.
Engine power needed—Approximate engine rating required.

Formula
P [kW] = F [kN] × v [km/h] / 3.6

Worked example: cultivating 50 hectares

  1. A 6 m cultivator at 10 km/h and 75% efficiency covers 6 × 10 × 0.75 / 10 = 4.5 ha an hour.
  2. 50 ha therefore takes about 11 hours.
  3. At 25 L/h the tractor uses 5.6 L per hectare — 6.67 per hectare at 1.20 per litre.
  4. A 30 kN draught at 8 km/h needs 67 kW at the drawbar, so about 100 kW of engine.

Typical field efficiency and speeds

OperationField efficiencyTypical speed
Ploughingabout 70 – 90%about 6 – 10 km/h
Disc harrowingabout 70 – 90%about 8 – 12 km/h
Seed drillingabout 65 – 85%about 8 – 14 km/h
Sprayingabout 55 – 75%about 10 – 16 km/h
Combine harvestingabout 65 – 80%about 5 – 8 km/h

Related

Machine ownership and operating cost calculatorBSFC, fuel flow and engine efficiency calculatorGenerator size, kVA and fuel consumption calculatorMachinery specifications

About these results

Results are theoretical estimates from standard engineering formulas. Real-world figures depend on conditions these formulas do not capture. Always follow the manufacturer's specifications for maintenance, loading and safety decisions.

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