A seed rate calculator determines how many pounds of seed you need per acre based on crop type, germination rate, and seed purity. Whether you are planting corn, soybeans, wheat, or pasture grass, getting the seeding rate right is critical for achieving optimal plant populations without wasting expensive seed. This tool shows total seed needed, bag count, and an estimated cost for your entire planting area.
Seed Rate & Cost Estimator
Adjust within the recommended range for your crop
Total acres to plant with this crop
From seed tag or test; default 92%
Percentage of viable seed; default 98%
Standard bag weight from your supplier
Price per bag from your dealer
Standard Seed Rates Reference
| Crop | Low Rate | High Rate | Unit |
|---|---|---|---|
| Corn | 20 | 35 | lbs/acre |
| Soybeans | 50 | 70 | lbs/acre |
| Winter Wheat | 90 | 120 | lbs/acre |
| Spring Wheat | 80 | 100 | lbs/acre |
| Oats | 64 | 96 | lbs/acre |
| Barley | 72 | 96 | lbs/acre |
| Alfalfa | 15 | 25 | lbs/acre |
| Clover (Red) | 8 | 12 | lbs/acre |
| Rye (Cereal) | 84 | 112 | lbs/acre |
| Grass (Lawn) | 3 | 8 | lbs/1000 sqft |
| Sunflower | 3 | 5 | lbs/acre |
| Cotton | 12 | 18 | lbs/acre |
| Rice | 80 | 120 | lbs/acre |
How to Use the Seed Rate Calculator
Getting your seeding rate right is one of the most important decisions in crop production. Plant too thin and you lose yield potential; plant too thick and you waste expensive seed while increasing competition between plants. This seed rate calculator takes the guesswork out of the equation by computing exactly how many pounds of seed you need based on your acreage, target rate, seed quality, and packaging.
Step 1: Select Your Crop
Choose from 13 common crops including corn, soybeans, winter and spring wheat, oats, barley, alfalfa, clover, cereal rye, grass seed, sunflower, cotton, and rice. Each crop comes pre-loaded with a recommended seeding rate range based on standard agricultural extension data. The slider adjusts within that range so you can fine-tune for your conditions.
Step 2: Set Your Seeding Rate
Use the slider or type a value to set your target seeding rate in pounds per acre. The range shown reflects the typical low-to-high recommendations for the selected crop. A rate at the lower end of the range is common for dryland farming or wide row spacing, while higher rates suit irrigated fields or narrow rows where you want a thicker stand.
Step 3: Enter Your Planting Area
Type the total acres (or square feet for grass) you plan to plant. The calculator multiplies your per-unit rate by the area to determine the total pounds of seed needed. This works for anything from a small garden plot to thousands of acres of commercial farmland.
Step 4: Adjust Germination and Purity
Every bag of certified seed has a tag listing the germination rate and purity percentage. Germination tells you what percentage of seeds will actually sprout, while purity indicates the fraction of the bag that is live seed versus inert matter. The calculator divides your base rate by these factors so you end up ordering enough viable seed. Default values of 92% germination and 98% purity are typical for quality certified seed.
Step 5: Set Bag Size and Cost
Enter the bag weight and price from your seed dealer. The calculator divides total seed by bag size and rounds up to give you the number of bags to order — because you can't buy a partial bag. Multiply by cost per bag for a quick budget estimate before you place your order.
Tips for Accurate Planning
Always use the actual germination and purity values from your seed tag rather than the defaults. If you are planting older seed, get a fresh germination test since viability drops over time. For precision planters, convert pounds per acre to seeds per acre using your seed's thousand-kernel weight. Consult your local extension office or seed dealer for variety-specific rate recommendations in your growing region.
FAQ
Is this seed rate calculator free to use?
Yes, the seed rate calculator is completely free with no signup, no account, and no hidden fees. All calculations run locally in your browser so your farm data stays private on your device.
Is my farm data safe when I use this tool?
Absolutely. Every calculation runs locally in your browser using client-side JavaScript. No acreage figures, crop selections, or cost data are ever sent to a server or stored anywhere.
How does germination rate affect the seeding rate?
Lower germination rates mean more seed is needed to achieve the same target plant population. If your seed tests at 85% germination instead of 95%, the calculator increases the seeding rate proportionally so you still end up with enough live plants per acre.
What is seed purity and why does it matter?
Seed purity measures the percentage of the seed lot that is actually viable seed, not inert matter or weed seeds. Most certified seed has 98-99% purity. Lower purity means you need more seed by weight to achieve the same effective seeding rate.
How many pounds of corn seed do I need per acre?
Corn typically requires 20 to 35 pounds of seed per acre depending on your target plant population (28,000 to 36,000 seeds per acre) and seed size. This calculator lets you adjust the rate within that range and accounts for germination and purity.
What is the standard bag size for seed?
The calculator defaults to 50-pound bags, which is the most common bulk packaging for many crops. You can change the bag size to match your supplier's packaging, whether that is 25-pound, 50-pound, or any other weight.
Can I use this for lawn and pasture grass seed?
Yes, the calculator includes a Grass (Lawn/Pasture) option with rates in pounds per 1,000 square feet. Enter your area and the calculator converts appropriately. For large pastures, enter total acreage and the tool scales the rate.
How accurate are these seeding rate recommendations?
The rates are based on standard agricultural extension recommendations for each crop. Actual optimal rates vary by seed variety, planting method, row spacing, soil conditions, and regional climate. Always cross-reference with your seed dealer or local extension office for variety-specific recommendations.