Garden calculator
Grass Seed Calculator
Calculate seed weight and bags from the area and the application rate printed for your task.
Planning estimate, not a contractor quote. Review the assumptions and replace presets with local prices when available.
Method
How this calculator works
New lawn establishment and overseeding can have different label rates even for the same seed blend. Select the appropriate rate before measuring out seed. The calculator reports the amount to apply and the bags to buy separately, leaving package surplus visible.
Seed lb = length × width ÷ 1,000 × label rate in lb per 1,000 ft². Bags = ceil(seed lb ÷ bag lb).
Worked example
A realistic starting point
A 50 × 40 ft lawn is 2,000 ft². At an illustrative label rate of 5 lb per 1,000 ft², it needs 10 lb of seed: two 5 lb bags. At a rate of 3 lb, the same area needs 6 lb and still requires two complete 5 lb bags.
What changes the answer
Factors worth checking
Choose the task-specific rate
Read the label for the blend and for new seeding or overseeding. Do not treat a general online rate as interchangeable across products.
Keep coverage consistent
Exclude hardscape from the lawn area. For several lawn sections, measure each area and add the square feet before calculating the total purchase.
Weigh the application
The remaining contents of a purchased bag are surplus, not an instruction to spread extra seed. Follow the label for the actual application and storage of leftovers.
Common questions
Grass Seed FAQ
Why can one seed bag cover different areas?
Product labels may state separate coverage for new lawns and overseeding. Match the rate to your actual use.
Can I calculate metric seed quantities?
Yes. Switch to metric and enter kg per 100 m² with bag weight in kg.
Does the price include soil preparation?
No. The seed total covers whole bags at the entered price. Prepare a separate budget for other work.
Evidence
Sources & review
- Pennington — Smart Seed Sun and ShadeExample of product-specific coverage that differs between new seeding and overseeding.
Published by Calcstead. Report a correction.
Method and source links reviewed September 6, 2026. Price presets are editable planning inputs and should be replaced with current local information.