🌱 Agriculture
Seed Rate Calculator
Convert a target plant population into a seed rate in lb/acre, kg/ha and seeds per foot of row. Enter the crop parameters, then press Convert.
About the Seed Rate Calculator
A target population is plants, but you buy seeds. The gap between the two is germination and field emergence. If 95% of seeds germinate and 90% of those emerge, you need about 1.17 seeds for every plant you want — a 17% seeding-rate increase before any losses from birds, disease or crusting.
Thousand-kernel weight (TKW) converts seed count into weight. Wheat is often 35–45 g per 1,000 kernels, so a 30,000 plants/acre target lands around 40–50 lb/acre after germination. Row spacing then sets the seeds per foot; the same population in 15-inch rows has twice the seeds per foot of 30-inch rows.
How the calculation works
- Seeds/acre = target plants/acre ÷ (germination × emergence).
- Weight (g/acre) = seeds/acre × TKW ÷ 1,000.
- lb/acre = g/acre ÷ 453.59237; kg/ha = lb/acre × 1.12085.
- Seeds/ft = seeds/acre × row spacing (ft) ÷ 43,560.
Reference values
| Crop | Typical TKW | Typical target |
|---|---|---|
| Wheat | 35–45 g | 1.2–1.8 million plants/acre |
| Barley | 38–48 g | 1.0–1.5 million |
| Oats | 30–40 g | 1.0–1.5 million |
| Soybeans | 150–200 g | 100,000–150,000 |
| Corn | 250–350 g | 28,000–36,000 |
Worked example: wheat at 1.5 million plants per acre
A target of 1.5 million plants/acre with 95% germination and 90% emergence needs 1.5M ÷ 0.855 = 1.754M seeds/acre. At a 40 g thousand-kernel weight, that is 70.2 kg/acre, or 155 lb/acre. In 30-inch rows, the seed rate is 1.754M × 2.5 ÷ 43,560 = 100.7 seeds per foot.
Those losses are multiplicative, not additive: 95% germination followed by 90% emergence leaves 85.5% of the seeds. Using only the lab germination figure overstates the stand. Recalculate with your own seed lot and field conditions rather than relying on a generic target.
Seed lots, germination tests and field conditions
A germination percentage is a property of a specific seed lot, not of a crop. Two bags of the same variety can differ by ten points if one has been stored warm or for longer, so the figure on the label should be read from the lot you are actually drilling. A test older than a year is a weak guide because germination declines in storage.
Field emergence adds soil temperature, moisture, seedbed condition and depth to the calculation. Cold, wet soil slows emergence and gives disease more time to act, which is why a population target that works in good conditions can fall short in a late sowing. Record the established plant count after emergence and use it to adjust the rate for the next field.