About the Seeding Rate Calculator
This seeding rate calculator works backward from the plant stand you want to the amount of seed to put in the drill or planter. Enter the target population in plants per acre, the germination percentage and purity from the seed tag, an expected field emergence (survival) percentage and the number of seeds per pound, and it returns seeds per acre, pounds of bulk seed per acre, seeds per foot of row and the total seed, bags and cost for your field.
It works for soybeans, small grains such as wheat, oats and barley, forage and cover-crop mixes, pasture grasses and food plots. Calculating by seeds rather than by a fixed pounds-per-acre rate matters because seed size varies a lot between varieties and seed lots — a lot with large seeds needs more pounds to deliver the same number of plants.
Field emergence depends on seedbed, soil temperature and moisture, planting depth and equipment; 80–90% is common for well-planted row crops in good conditions, while broadcast seeding or poor conditions can drop much lower. Check seed-tag numbers for each lot and follow local agronomic recommendations for target populations.
With the default inputs, the seeding rate is 66 lb/acre. Change any value above to recalculate instantly.
How to use the seeding rate calculator
- 1Enter the plant population you want to establish per acre.
- 2Copy germination, purity and seeds per pound from the seed tag.
- 3Estimate field emergence for your conditions and planting method.
- 4Enter row spacing (or 0 for broadcast) and the field size.
- 5Enter bag weight and price to see bags to buy and cost.
Formula and method
Not every seed you plant becomes a plant. Germination (from the seed tag) is the share that sprouts in lab conditions, and field emergence is the share of those that actually establish in your field. Dividing the target stand by both gives the number of seeds to plant per acre.
Bulk seed also contains inert matter and other seeds, so the pounds needed equal seeds per acre divided by seeds per pound times purity. Purity × germination is the pure live seed (PLS) percentage. Seeds per foot of row multiplies seeds per square foot (seeds per acre ÷ 43,560) by the row width in feet. Total seed is the rate times the field area, rounded up to whole bags.
- Target
- Desired established plants per acre
- Germination
- Seed-tag germination as a decimal
- Emergence
- Expected field emergence / survival as a decimal
- Purity
- Seed-tag purity as a decimal
Worked examples
Soybeans: 140,000 plants/acre in 15-inch rows
To end with 140,000 plants at 90% germination and 85% emergence you must plant 140,000 ÷ 0.765 ≈ 183,000 seeds per acre. At 2,800 seeds per pound and 99% purity that is about 66 lb/acre, or 5.25 seeds per foot of 15-inch row. Eighty acres need about 5,282 lb — 106 fifty-pound bags.
Winter wheat at 1.3 million plants/acre
About 30 plants per square foot requires 1.71 million seeds per acre after 95% germination and 80% emergence. At 14,000 seeds per pound and 98% purity the rate is about 125 lb/acre, or 24.5 seeds per foot of 7.5-inch drill row; 40 acres take 100 bags.
Half-acre broadcast cover crop
Broadcast seeding has lower emergence, so 500,000 plants per acre needs about 840,000 seeds. At 6,000 seeds per pound and 95% purity that is roughly 147 lb/acre, or 74 lb for half an acre — three 25-lb bags.
Frequently asked questions
How do I calculate seeding rate in pounds per acre?+
Divide the target plants per acre by germination and by expected emergence to get seeds per acre, then divide by seeds per pound and by purity. For example 140,000 ÷ (0.90 × 0.85) ÷ (2,800 × 0.99) ≈ 66 lb per acre.
What is pure live seed (PLS)?+
Pure live seed is the share of a bag that is viable seed of the species you want: purity × germination. Seed at 99% purity and 90% germination is 89.1% PLS, so 100 lb of bulk seed holds 89.1 lb of pure live seed.
Why plant by seeds per acre instead of pounds?+
Seed size varies between varieties and lots, sometimes by 30% or more. A fixed pounds-per-acre rate can therefore deliver very different plant stands, while planting to a seed count gives a consistent population.
What field emergence should I assume?+
Well-planted row crops in a good seedbed often reach 80–90% emergence, drilled small grains around 70–85%, and broadcast or no-till seedings into residue can be 50–70%. Use your own stand counts from past seasons when you have them.
How do I check my plant population after emergence?+
For rows, count plants in a length of row equal to 1/1,000 of an acre (17 ft 5 in for 30-inch rows, 34 ft 10 in for 15-inch rows) and multiply by 1,000. Repeat in several spots and average.