Loading the page...
Preparing tools and content for you. This usually takes a second.
Preparing tools and content for you. This usually takes a second.
Fetching calculator categories and tools for this section.
Free garden fertilizer calculator for beds and plots. Enter area, a target nitrogen rate per 1,000 sq ft, and your bag's N-P-K analysis. We compute pounds of product and the P₂O₅ and K₂O that come along at that nitrogen-led rate.
Last updated: April 8, 2026
Need a branded grow planner for your site? Get a Quote
Common maintenance vegetable beds often use roughly 0.5–2 lb N/1000 sq ft per application depending on soil test—adjust for your plan.
Use the three numbers printed on the product (e.g. 10-10-10).
Leave 0 to hide bag count; we only use it to estimate whole bags.
Total N to apply
0.4 lb
Fertilizer product needed
4 lb
P₂O₅ applied (with that product rate)
0.4 lb
K₂O applied (with that product rate)
0.4 lb
Whole bags to buy (rounded up)
1
Based on nitrogen rate. Follow label rates and local extension guidance for your crop.
Core idea
lb product = lb N ÷ (N%)
Works for synthetic blends and labeled organics.
Total N
(Area ÷ 1000) × rate
Match the rate to your soil test or crop plan.
Carry-through
Product × P% and K%
Compare to recommendations if you are managing P or K tightly.
Retail sizes
ceil(lb ÷ bag lb)
Round up so you have enough for the pass.
You control the rate
Editable N / 1000
Turf and beds rarely share the same program—set the rate accordingly.
Best practice
Test & comply
Follow maximum application rates on the product and local regulations.
400 sq ft, 1 lb N per 1,000 sq ft, 10-10-10 fertilizer, 40 lb bags:
Product needed
4.0 lb
Bags (rounded up)
1
Granular fertilizers list N-P-K as percent by weight. If you know how much nitrogen you want to deliver per unit area, you can back-solve the pounds of product: divide total nitrogen required by the decimal nitrogen fraction in the blend.
lb N needed = (sq ft ÷ 1,000) × (lb N per 1,000 sq ft)lb product = (lb N needed) ÷ (N% ÷ 100)lb P₂O₅ applied = lb product × (P% ÷ 100)lb K₂O applied = lb product × (K% ÷ 100)This is standard agronomic product math for a single application pass; split applications use the same idea per pass.
Nitrogen moves through soil quickly; phosphorus and potassium accumulate. Your county extension or lab report tells you whether to emphasize N, balance P/K, or amend with other materials.
Planning layout? Use our plant spacing calculator and raised bed soil calculator.
Get a Custom Calculator for Your SiteVerify against your soil test before applying extra P in phosphorus-sensitive sites.
Share it with other gardeners planning feeding schedules
Suggested hashtags: #Gardening #Fertilizer #NPK #VegetableGarden #Calculator