Plant Population Calculator (plants per hectare & acre from row spacing)

Understanding the plant population calculator — concept and principle

This calculator finds plants per hectare and per acre from row spacing and in-row spacing, the seeds to sow allowing for emergence, the total seed for a field, plants per metre or foot of row, and the in-row spacing needed for a target population. Farmers and agronomists use it to set planters and check stands.

Each plant gets a 75 × 18 cm patch; extra seed covers the 5 % that never emerge.

How it is calculated

Plants per hectare = 10,000 m² ÷ (row spacing × in-row spacing, in metres)

Plants per acre = 43,560 ft² ÷ (row spacing × in-row spacing, in feet); 1 acre = 0.40469 ha

Seeds to sow = plants ÷ emergence

In-row spacing for a target = area per plant ÷ row spacing

Metric inputs in cm and hectares; imperial in inches and acres.

The principle

Each plant occupies a small rectangle of ground: row spacing one way, in-row spacing the other. Dividing the field area by that rectangle gives the number of plants. Not every seed emerges, so you sow more seeds than the plant target, in proportion to expected emergence. Reversing the calculation gives the spacing needed for a chosen population.

Worked example

Default inputs: metric, rows 75 cm, in-row 18 cm, emergence 95%, field 10 ha, target 80,000 plants/ha.

Area per plant = 0.75 × 0.18 = 0.135 m², so 74,074 plants/ha = 29,977 plants/acre.
Seeds per hectare = 74,074 ÷ 0.95 = 77,973; for 10 ha 779,728 seeds.
Plants per metre of row = 1 ÷ 0.18 = 5.56 (1.69 per foot).
For 80,000/ha: spacing = 10,000 ÷ (80,000 × 0.75) = 0.1667 m = 16.7 cm.

Each point is the calculator re-run with only “Row spacing (between rows)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Row spacing (between rows)	Plants per hectare
18.8	296,296
37.5	148,148
56.2	98,765
75	74,074
93.8	59,259
112	49,383
150	37,037

How to read the result

Compare with the population recommended for your crop, hybrid, soil and rainfall; recommendations vary widely between regions. A stand count after emergence, using a set length of row, shows whether the achieved population matches the plan.

Common mistakes

Mixing cm with m, or inches with feet.
Forgetting emergence losses when buying seed.
Using total field area when headlands are not planted.

Keep in mind: Optimum populations depend on crop, variety, soil and climate. Follow local agronomic advice.

Frequently asked questions

How do I count plants in the field?

Count plants in a measured length of row and scale by row spacing.

Why sow more seeds than the target?

Some seeds do not emerge.

How many square feet are in an acre?

43,560.

Does row spacing change the population?

Yes; narrower rows with the same in-row spacing mean more plants.

Sources: R. L. Nielsen, "Estimating Corn Grain Yield Prior to Harvest", Purdue University Agronomy Dept. (rev. 2021)

Checked 9 Nov 2026. Area per plant = row spacing × in-row spacing; acre of 43,560 ft² as used for the 1/1000-acre row length in Nielsen R.L., “Estimating Corn Grain Yield Prior to Harvest”, Purdue University Agronomy Dept. (rev. 2021). 1 acre = 4,046.8564224 m² (international foot).

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