Seed Germination Rate Calculator
Knowing your seed germination rate before planting prevents the disappointment of sparse stands and wasted bed space. This calculator does two things: it computes the germination percentage from a test you have performed, and it works backward to tell you how many seeds to plant to achieve a target number of plants given that germination rate. Both calculations follow the standard formulas used in USDA Federal Seed Act testing and Cooperative Extension seed vigor publications. Enter your test results to get the germination rate, then enter your desired plant count to get the seeds to plant.
Seed germination formula
Germination rate (%) = (Seeds germinated / Seeds tested) x 100
Seeds to plant = Target plants / (Germination rate / 100)
Round seeds-to-plant up to the nearest whole number. Test a representative sample of at least 10 seeds for a reliable estimate; 25 to 100 seeds is recommended for accuracy.
Minimum germination rates by crop (USDA Federal Seed Act)
- Corn: 75% minimum (USDA Federal Seed Act).
- Alfalfa: 60% minimum.
- Kentucky bluegrass: 75% minimum.
- Soybean: 70% minimum.
- Tomato: 75% minimum (commercial standard).
- Carrot: 55% minimum (hard to germinate species).
Seed germination calculator: frequently asked questions
How do I calculate seed germination rate?
Germination rate = (number of seeds that germinated / total seeds tested) x 100. For example, if 85 of 100 seeds germinate, the rate is 85 percent.
How many seeds should I plant to account for germination rate?
Divide your target plant count by the germination rate (as a decimal). If you want 100 plants and germination is 80 percent: 100 / 0.80 = 125 seeds needed. This accounts for seeds that will not sprout.
What is the minimum acceptable seed germination rate?
The USDA Federal Seed Act sets minimum germination standards by species. For example, corn must meet 75 percent, alfalfa 60 percent, and Kentucky bluegrass 75 percent minimum germination to be labeled and sold. High-quality commercial seed typically exceeds 85 to 90 percent.
How do I perform a germination test at home?
Place a known number of seeds (typically 10 to 25) on a moist paper towel. Fold and place in a plastic bag at the temperature recommended for the species (most vegetables: 65 to 75 degrees Fahrenheit). Count germinated seeds after the number of days listed on the seed packet for germination.
Does germination rate affect planting cost?
Yes. Lower germination rates require more seed to achieve the same stand, increasing seed cost. If germination falls below 60 percent, it is often more economical to purchase fresh seed than to plant extra old seed, especially for crops where stand establishment is critical.
Official sources
- USDA Agricultural Marketing Service, Federal Seed Act: ams.usda.gov.
- USDA NIFA, seed quality resources: nifa.usda.gov.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.