acalculator

What will my corn yield be?

Count the ears in a length of row and the kernels on a few ears. The corn yield calculator estimates grain yield in bushels per acre (and tonnes per hectare) by the yield component method.

Your numbers

Units
Optional. Empty means 1/1000 acre of row.
65 heavy kernels, 85 light; 90 to 100 under stress.
Estimated yield
180.7

Your corn should yield about 180.7 bushels per acre.

Estimated yield (metric)
11.34
Ears per acre
30,000
Kernels per ear
512
Row length for 1/1000 acre
17.42 ft

Estimated yield: 180.7. Your corn should yield about 180.7 bushels per acre.

Estimated yield by kernel weight factor

How to calculate

Estimates corn grain yield in bushels per acre before harvest by the yield component method: ears in a length of row, kernel rows and kernels per row, and a kernel weight factor, with tonnes per hectare.

Example with the default inputs (Row width 30 in, Harvestable ears in that length 30, Kernel rows per ear 16, Kernels per row 32, Kernel weight factor 85): Your corn should yield about 180.7 bushels per acre.

Method: Bushels per acre = ears per acre × (kernel rows × kernels per row) ÷ (kernel weight factor × 1,000); ears per acre = ears counted × 43,560 ft² ÷ (row length × row width).

  • The kernel weight factor stands for kernel size: 65 for heavy kernels, 85 for light ones, 90 to 100 after a stressful grain fill.
  • Purdue says the method is probably only accurate within about 20 bushels per acre; count several spots in the field.
  • Tonnes per hectare use the 56 lb bushel of shelled corn.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Row width 30 in, Harvestable ears in that length 30, Kernel rows per ear 16, Kernels per row 31.9375, Kernel weight factor 75 gives Estimated yield 204.4, Ears per acre 30,000, Kernels per ear 511, Estimated yield (metric) 12.829711.Source: Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (bushels per acre = ears per acre × average kernels per ear ÷ a kernel weight factor in thousands; 17.4 ft of 30-inch row is 1/1000 acre; factors of 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac), https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03); Iowa State University Extension, Ag Decision Maker C6-80, Metric Conversions (corn with a 56-pound bushel: 1 bushel per acre = 0.0628 metric tons per hectare), https://www.extension.iastate.edu/AGDm/wholefarm/html/c6-80.html (retrieved 2026-10-03)
  2. Row width 30 in, Harvestable ears in that length 30, Kernel rows per ear 16, Kernels per row 31.9375, Kernel weight factor 85 gives Estimated yield 180.352941, Row length for 1/1000 acre 17.42 ft.Source: Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (bushels per acre = ears per acre × average kernels per ear ÷ a kernel weight factor in thousands; 17.4 ft of 30-inch row is 1/1000 acre; factors of 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac), https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03)
  3. Row width 36 in, Length of row counted 20 ft, Harvestable ears in that length 25, Kernel rows per ear 16, Kernels per row 30, Kernel weight factor 85 gives Ears per acre 18,150, Estimated yield 102.494118, Estimated yield (metric) 6.433316.Source: Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (bushels per acre = ears per acre × average kernels per ear ÷ a kernel weight factor in thousands; 17.4 ft of 30-inch row is 1/1000 acre; factors of 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac), https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03); Iowa State University Extension, Ag Decision Maker C6-80, Metric Conversions (corn with a 56-pound bushel: 1 bushel per acre = 0.0628 metric tons per hectare), https://www.extension.iastate.edu/AGDm/wholefarm/html/c6-80.html (retrieved 2026-10-03)

How it works

With the row width W, the length of row counted L (in the same length unit), the ears counted E, the kernel rows per ear R, the kernels per row K and the kernel weight factor F:

  • Ears per acre = E × 43,560 ft² ÷ (L × W). When L is left empty, L is 1/1000 acre of row (43,560 ÷ W ÷ 1,000), so ears per acre = E × 1,000.
  • Kernels per ear = R × K.
  • Estimated yield (bushels per acre) = ears per acre × kernels per ear ÷ (F × 1,000). F is the thousands of kernels in a bushel.
  • Estimated yield (tonnes per hectare) = bushels per acre × 56 lb × 0.45359237 kg/lb ÷ 4,046.8564224 m² × 10,000 m²/ha ÷ 1,000 kg/t (about × 0.0628).
  • Row length for 1/1000 acre = 43,560 ft² ÷ W ÷ 1,000.

Rules. Row width is from 5 cm to 5 m; the length of row, when typed, is from 10 cm to 10 km. Ears are above 0 and at most 100,000; kernel rows above 0 and at most 40; kernels per row above 0 and at most 100; the factor from 50 to 120. A yield above 1,000,000 bu/ac has no answer. In Metric, the page heads the result with tonnes per hectare.

Exact arithmetic. Typed values are exact decimals (1 ft = 0.3048 m and 1 in = 0.0254 m exactly), so the result is an exact fraction, rounded once for display.

Output format. Bushels per acre show 1 decimal, tonnes per hectare 2, ears per acre 0, kernels per ear 1, and the row length 2 decimals in feet (or metres).

Worked examples by hand

Purdue’s example: 30 ears in 1/1000 acre of 30-inch rows, 511 kernels per ear (16 rows × 31.9375), factor 75. Ears per acre = 30 × 1,000 = 30,000. Yield = 30,000 × 511 ÷ 75,000 = 204.4 bu/ac, Purdue’s 204. In tonnes: 204.4 × 56 × 0.45359237 ÷ 4,046.856 × 10 = 12.83 t/ha.

The same ears at factor 85. 30,000 × 511 ÷ 85,000 = 180.4 bu/ac, Purdue’s 180. The row length for 1/1000 acre at 30 inches is 43,560 ÷ 2.5 ÷ 1,000 = 17.42 ft.

25 ears in 20 ft of 36-inch rows, 16 rows × 30 kernels, factor 85. Ears per acre = 25 × 43,560 ÷ (20 × 3) = 18,150. Kernels per ear = 480. Yield = 18,150 × 480 ÷ 85,000 = 102.5 bu/ac, or 6.43 t/ha.

Other questions people ask

How do I estimate corn yield before harvest?

Count the harvestable ears in 1/1000 acre of row (17.4 ft of 30-inch rows). On every fifth ear in the row, count the kernel rows and the kernels per row. Then bushels per acre = ears per acre × kernels per ear ÷ (kernel weight factor × 1,000).

What kernel weight factor should I use?

Purdue’s Bob Nielsen suggests working out the yield with factors of 65, 75 and 85 in a normal season; a lower factor means heavier kernels and a higher yield. After a stressful grain fill, use 90 to 100. The default here is 85, the cautious end of the normal range.

How long a row is 1/1000 acre?

Divide 43,560 sq ft by the row width in feet, then by 1,000. For 30-inch rows that is 43,560 ÷ 2.5 ÷ 1,000 = 17.4 ft; for 36-inch rows, 14.5 ft; for 20-inch rows, 26.1 ft. Leave the length empty and the calculator uses this length.

How accurate is the estimate?

Purdue says it is probably accurate only within about 20 bushels per acre, mostly because kernel weight is a guess until the grain is mature. Count several spots that stand for the whole field and average them.

Which kernels should I count?

Purdue says to leave out the extreme butt and tip kernels: start and end where there are complete rings of kernels around the cob, and do not count aborted kernels. If the row number changes along a pinched ear, use an average.

How do bushels per acre convert to tonnes per hectare?

A bushel of shelled corn weighs 56 lb, so 1 bu/ac is about 0.0628 t/ha. 200 bu/ac is about 12.55 t/ha.