Seeding rate calculator
Enter the plant population you want at harvest, the germination rate from the seed tag and how many seedlings you expect to survive in the field. Add the seed size, the field area and the row spacing: the calculator returns the seeding rate, the seed to buy and how far apart the planter should drop the seeds.
Runs in your browser: nothing you enter is sent anywhere.
How to use
- Choose US or metric units and enter the target plant population.
- Enter the germination rate and the share of seedlings you expect to survive.
- Enter the seed size (seeds per pound, or 1,000-seed weight in grams), the field area and the row spacing.
How it works
- seeds per area = target plants ÷ (germination × survival);
- US: lb per acre = seeds per acre ÷ seeds per pound;
- metric: kg per ha = seeds per ha × 1,000-seed weight (g) ÷ 1,000,000;
- seed for the field = rate × area;
- spacing in the row = 1 ÷ (seeds per unit area × row spacing).
Example
Corn for 32,000 plants per acre, 95 % germination, 90 % survival, 1,600 seeds per pound, 25 acres in 30-inch rows:
- 32,000 ÷ (0.95 × 0.90) = 37,427 seeds per acre;
- 37,427 ÷ 1,600 = 23.4 lb per acre; × 25 acres = 584.8 lb;
- an acre is 6,272,640 in²; ÷ 37,427 = 167.6 in² per seed; ÷ 30 in = 5.6 in between seeds.
Metric: 80,000 plants/ha with the same percentages and 300 g per 1,000 seeds gives 93,567 seeds/ha, 28.1 kg/ha and 14.3 cm between seeds in 75 cm rows.
Tips and common mistakes
- Enter percentages as percentages (95, not 0.95).
- The target is the stand at harvest, not the number of seeds; do not apply the loss twice.
- For small-grain crops sown in narrow rows, the spacing in the row is short; the rate per area matters more.
Frequently asked questions
How do you calculate seeding rate?
Divide the plant stand you want by the share of seeds that will become plants: seeds = target plants ÷ (germination × survival). Then convert seeds to weight with the seed size: by seeds per pound, or by the weight of 1,000 seeds.
What is field survival or emergence?
Germination on the tag is measured in a lab under ideal conditions. In the field some seeds rot, are eaten or fail to break through, so fewer emerge. Growers often allow 5–15 % for this, more in cold or cloddy seedbeds.
Where do I find seeds per pound or the 1,000-seed weight?
On the seed bag or tag for many crops, or from your seed supplier. Seed size varies between varieties and lots, so using the figure of your own seed lot is more accurate than a general average.
How is the seed spacing worked out?
The area per seed is the field area divided by the number of seeds. Dividing that by the row spacing gives the distance between seeds along the row.