Fertilizer calculator
The label says lb per 1,000 ft², your lawn is whatever size it is. Pick your product and get the pounds and bag count — plus what the numbers on the bag actually mean.
Fertilizer needed
How much fertilizer do I need?
Granular fertilizer is dosed by lb of product per 1,000 ft², printed on the bag. Multiply by your lawn area and divide by 1,000:
Worked example: a 2,400 ft² lawn at 3.1 lb/1k (16-4-8, half-pound N rate) needs 7.4 lb — a single 20 lb bag covers three applications.
Working from the nitrogen number
Extension services dose by lb of actual N per 1,000 ft² — usually 0.5–1 lb per application. To turn that into product:
Want 1 lb N from 16-4-8? 1 ÷ 0.16 = 6.3 lb of product per 1,000 ft². From 10-10-10? 1 ÷ 0.10 = 10 lb. That's why the "same" nitrogen rate means very different bag weights on different products.
Typical rates
| Product / situation | Rate (product per 1k ft²) | Season |
|---|---|---|
| 16-4-8 lawn food, maintenance (0.5 lb N) | 3.1 lb | every 6–8 weeks in growth |
| 16-4-8, max annual (1 lb N) | 6.3 lb | 1–2× per season |
| Starter fertilizer at seeding | 5 lb | once, at sowing |
| 10-10-10 vegetable garden | 10–15 lb | before planting + side-dress |
Spreader notes
Set your broadcast spreader to the low end of the bag's chart, walk at a steady pace, and always close the hopper at row ends. Water in granular fertilizer within 24–48 hours — the N only becomes plant-available after it dissolves. Never apply to frozen ground or before heavy rain.