Liquid Fertilizer Calculator
Three calculators in one: calculate how much liquid fertilizer to buy (oz and gallons), tank mixing ratios (oz per tank fill), and hose-end sprayer concentrate settings. Covers 20-20-20, Miracle-Gro, Peters, fish emulsion, kelp, and custom NPK.
20% N · 20% P · 20% K · density 9.6 lbs/gal
Results
Tip: Liquid fertilizers are fast-acting (absorbed in 24–48 hours) but short-lasting (2–4 weeks). Use slow-release granular for maintenance and liquid for quick green-up or foliar feeding.
Liquid Fertilizer Dilution Guide
Converting from weight-based nutrient rates to volume-based mixing instructions requires density:
Common Liquid Fertilizer Mixing Rates
| Fertilizer | NPK | Density | Oz/1,000 sqft (0.5 lb N) | Oz/1,000 sqft (1 lb N) |
|---|---|---|---|---|
| 20-20-20 | 20-20-20 | 9.6 lbs/gal | 33 oz | 67 oz |
| 10-10-10 | 10-10-10 | 9.2 lbs/gal | 70 oz | 139 oz |
| Miracle-Gro | 24-8-16 | 9 lbs/gal | 28 oz | 56 oz |
| Peters 20-10-20 | 20-10-20 | 9.5 lbs/gal | 34 oz | 68 oz |
| Fish Emulsion | 5-1-1 | 8.8 lbs/gal | 146 oz | 291 oz |
| Kelp 2-0-4 | 2-0-4 | 8.5 lbs/gal | 379 oz | 758 oz |
Frequently Asked Questions
How much liquid fertilizer per gallon of water?
It depends on the fertilizer and application rate. For Miracle-Gro 24-8-16 at 1 lb N per 1,000 sq ft: using density 9.0 lbs/gal → product needed per 1,000 sq ft = 1 ÷ 0.24 = 4.17 lbs = 4.17 ÷ 9.0 = 0.46 gallons = 59 oz. Divide by coverage rate to get oz per gallon. Typical hand-spray rates: 1-4 oz per gallon for foliar feeding.
How do I calculate liquid fertilizer dilution?
Dilution formula: oz per gallon = (N rate × coverage) ÷ (N% × density × total water). For tank mixers: Product oz per tank = oz-per-gallon × tank size. Our Tank Mixing tab does this automatically — enter your fertilizer, area, and desired N rate to get oz per tank fill.
What is the hose-end sprayer fertilizer calculator setting?
Hose-end sprayers have a concentrate dial (typically 1, 2, 3, 4 oz/gallon of output). To calculate: Total water needed (gal) = Area ÷ 1,000 × 100 gal (standard lawn rate). Concentrate needed (oz) = setting × total water. Example: 5,000 sq ft, 2 oz setting, 100 gal/1,000 sqft rate: Total water = 500 gal; Concentrate = 2 × 500 = 1,000 oz (7.8 gallons).
How much liquid fertilizer per 1,000 square feet?
At 1 lb N per 1,000 sq ft with 20-20-20 fertilizer (density 9.6 lbs/gal): Product lbs = 1 ÷ 0.20 = 5 lbs. Product gallons = 5 ÷ 9.6 = 0.52 gal = 66 oz per 1,000 sq ft. At 0.5 lb N rate: 33 oz per 1,000 sq ft. Our 'How Much to Buy' tab calculates this with any fertilizer and any area.
Can I mix different liquid fertilizers together?
Generally yes, but check compatibility first. N+K fertilizers (e.g. 20-0-20) can usually be mixed. Phosphorus-rich fertilizers sometimes precipitate with calcium or sulfur sources. Never mix concentrated products directly — add each to the tank water separately (wash, fill, fertilizer A, fertilizer B method). Our tank mix tab shows product oz per tank for safe application rates.
What is the difference between 20-20-20 and Miracle-Gro 24-8-16?
20-20-20 (equal NPK) is a balanced all-purpose fertilizer — good for general garden use. Miracle-Gro 24-8-16 has high N and K with lower P — better for established plants and lawns that already have sufficient phosphorus. 20-20-20 has slightly higher density (9.6 vs 9.0 lbs/gal). For lawns where P is adequate, 20-0-20 or 24-0-0 is more appropriate.
How do I convert liquid fertilizer lbs to gallons?
Gallons = lbs ÷ density (lbs/gal). Typical liquid fertilizer densities: water = 8.34, 20-20-20 ≈ 9.6, Miracle-Gro 24-8-16 ≈ 9.0, Peters 20-10-20 ≈ 9.5, fish emulsion 5-1-1 ≈ 8.8, kelp 2-0-4 ≈ 8.5. Then: oz = gal × 128. Our calculator uses actual density values for accurate volume calculations.
What is fish emulsion fertilizer and how much do I use?
Fish emulsion (typically 5-1-1) is an organic liquid fertilizer made from fish processing byproducts. It's slow-release, gentle, and improves soil biology. For lawns: 0.5 lb N per 1,000 sq ft every 4-6 weeks. Product rate = 0.5 ÷ 0.05 = 10 lbs per 1,000 sqft = 1.14 gal = 146 oz. Dilute heavily (2-3 oz per gallon) and apply as drench. Has a strong smell that dissipates in 1-2 days.