Why use this calculator
Calculating your seeding rate accurately is critical to achieving optimal plant populations and maximizing crop yields. Planting too few seeds results in poor field coverage and reduced harvests, while over-seeding wastes expensive seed and creates competition among plants. This calculator accounts for germination rates to ensure you achieve your target plant population, helping you order the right amount of seed and plan your planting operations with confidence.
How to use it
Select your preferred unit system (metric or imperial). Enter your total field area, the number of seeds per weight unit for your seed variety (found on the seed bag label), your desired plant population per area unit, and the germination percentage from your seed test. The calculator determines the seeding rate and total seed required for your entire field.
The formula
Seeding Rate = Desired Plants Per Area / (Seeds Per Weight Unit x Germination Rate / 100). Total Seed = Seeding Rate x Field Area. This formula adjusts for germination losses to ensure you achieve your target stand.
Worked examples
100-acre corn field with 15,000 seeds/lb, targeting 32,000 plants/acre at 92% germination
Seeding rate of 2.32 lbs/acre, requiring 231.88 lbs of seed total
200-acre soybean field with 2,500 seeds/lb, targeting 140,000 plants/acre at 88% germination
Seeding rate of 63.64 lbs/acre, requiring 12,727.27 lbs of seed total
When people use it
- Determining seed purchase quantities before planting season
- Calibrating planter settings for accurate seed delivery
- Adjusting seeding rates for varying germination test results
- Planning seed inventory for multi-field operations
Tips
- Always use a current germination test rather than the printed rate on older seed bags
- Increase seeding rate by 5-10% for no-till or challenging soil conditions
- Consider seed size variation within a lot, as seeds per pound can vary
- Keep records of actual plant stands to refine future seeding rate decisions
Questions people ask
- How do I find the seeds per pound for my variety?
- The seeds per pound count is typically printed on the seed bag label or available from your seed dealer. Common values include 1,300-1,800 for corn (kernel count basis), 2,500-3,500 for soybeans, and 12,000-18,000 for wheat. For precise calibration, you can count and weigh a sample yourself.
- What germination rate should I use?
- Use the germination percentage from the most recent seed test, which should be printed on the seed tag. If the seed is more than a year old, consider having it retested. Standard commercial seed typically has germination rates between 85% and 98%.
- Should I adjust for field emergence vs. germination?
- Yes, field emergence is usually 5-15% lower than lab germination due to soil conditions, pests, and weather. Many farmers use an estimated field emergence rate instead of lab germination for more realistic planting plans.