Lawn Math: How Much Seed, Sod, and Fertilizer Do You Need?
October 21, 2026
Every lawn product is rated per 1,000 square feet, so the first step is to measure your lawn area and subtract buildings, beds, and driveways. Break irregular shapes into rectangles, triangles, and circles, calculate each, and add them. A lawn that is 100 feet by 50 feet is 5,000 square feet. From there you can calculate how much seed, sod, or fertilizer to buy.
A little arithmetic prevents the common mistakes of buying too little to finish the job or applying too much fertilizer, which can burn the grass and pollute waterways.
Skip the math and get your answer instantly:
Open the Square Footage Calculator →Grass Seed
Application rates depend on the grass type and whether you are seeding a new lawn or overseeding. New cool-season lawns, such as fescue, bluegrass, and ryegrass, typically need 4 to 8 pounds of seed per 1,000 square feet, depending on species (tall fescue about 6 to 8, Kentucky bluegrass 2 to 3, and perennial ryegrass 6 to 8). Overseeding an existing lawn uses about half. For 5,000 square feet at 5 pounds per 1,000, you need 25 pounds. Warm-season seeds such as Bermudagrass use only 1 to 2 pounds per 1,000 square feet.
Check the bag for its recommended rate and the percentage of pure live seed. Buy a little extra for patching.
Sod
Sod is sold by the square foot, roll, or pallet. A pallet commonly covers 400 to 500 square feet, and a roll covers about 10 square feet (2 feet by 5 feet). For 5,000 square feet, 5,000 ÷ 450 = 11 pallets. Order 5% to 10% extra for cuts and irregular edges. Sod should be laid within 24 hours of delivery in hot weather, and watered immediately and often until the roots establish, usually over two weeks.
Sod costs more than seed up front, but it provides an instant lawn and fewer weeds in the first season.
| Material | Rate | For 5,000 sq ft |
|---|---|---|
| Tall fescue seed (new lawn) | 5 to 8 lb per 1,000 sq ft | 25 to 40 lb |
| Overseeding | 2.5 to 4 lb per 1,000 sq ft | 12 to 20 lb |
| Sod (pallet of 450 sq ft) | 1 pallet per 450 sq ft | 11 pallets + extra |
| Fertilizer (1 lb N per 1,000 sq ft) | 5 lb of nitrogen | 1 bag of 25 lb, 20-0-0 |
| Topsoil (1 inch layer) | 3.1 cubic yards per 1,000 sq ft | about 15.4 cubic yards |
Fertilizer and the Nitrogen Math
The three numbers on a fertilizer bag are the percentages by weight of nitrogen, phosphorus, and potassium (N-P-K). A 25-pound bag of 20-0-0 contains 25 × 0.20 = 5 pounds of nitrogen. Lawn guidelines often suggest about 1 pound of nitrogen per 1,000 square feet per application, with several applications a year depending on grass type. So one bag covers 5,000 square feet at 1 pound per 1,000.
To compute the amount of product for a desired nitrogen rate: product (lb) per 1,000 sq ft = target N rate ÷ N fraction. For 1 lb N with a 20% N product: 1 ÷ 0.20 = 5 lb per 1,000 square feet. With 30% N, 3.3 lb per 1,000.
Topsoil and Preparation
A new lawn needs 4 to 6 inches of loosened soil and a smooth, level surface. If you add a layer of topsoil, one cubic yard covers 324 square feet at 1 inch deep. For 5,000 square feet and 1 inch: 5,000 ÷ 324 = 15.4 cubic yards. A soil test tells you pH and nutrient needs and prevents wasted fertilizer. Spread seed evenly with a broadcast or drop spreader in two directions, rake lightly, and keep the surface moist until germination, which takes 1 to 3 weeks.
Timing
Plant cool-season grasses in early fall when soil is warm and nights are cooler, and warm-season grasses in late spring when soil temperatures stay above about 65°F. Avoid fertilizing during drought or heat stress, and never apply fertilizer just before heavy rain.
Frequently Asked Questions
How much grass seed do I need for 5,000 square feet?
Roughly 25 to 40 pounds for a new cool-season lawn, depending on species, and about half for overseeding.
How much does a pallet of sod cover?
Typically 400 to 500 square feet.
How do I calculate nitrogen in a fertilizer bag?
Multiply the bag weight by the first number, as a percentage. A 25 lb bag of 20-0-0 has 5 lb of nitrogen.
When is the best time to plant grass seed?
Early fall for cool-season grasses and late spring for warm-season ones.
How much topsoil covers a lawn?
One cubic yard covers about 324 square feet at 1 inch depth.