Nutrient Dose Calculator
How many mL of stock solution to dose a hydroponic reservoir up to your target ppm.
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Compost Tea & Liquid Dilution Calculator
Turn a product analysis and a target ppm nitrogen into millilitres per litre, ounces per gallon and a 1-to-n ratio for the tank you are mixing.
Compost Tea & Liquid Dilution Calculator
Chlorova · updated for 2026
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Nitrogen percentages are typical label analyses and vary by brand and batch, so re-measure against the bag or bottle you actually hold. The ppm figure is a target strength, not a safe level for every plant, and foliar tolerance drops sharply in heat, under strong light or on wet leaf that dries slowly. Test the mixed solution on a few leaves and wait two days, do not tank-mix acidic teas with copper or high pH products, and observe harvest intervals and any local rules on using urine as a fertilizer.
Liquid feeding lives or dies on the dilution, and the number on a label rarely matches the plant you are standing over. Too weak costs you a round of growth; too strong burns leaf edges and, in a hydroponic stock, locks out calcium. This calculator takes a product analysis and your target nitrogen strength and returns millilitres per litre, ounces per gallon and a one-to-n ratio for the tank in front of you, so you dose by whichever unit the sprayer actually uses.
Mixing a Tank to a Target Strength
- Choose the product, which sets its nitrogen percent.
- Enter the ppm nitrogen you want in the finished spray.
- Set tank volume in liters, not the amount you will use.
- Read millilitres per liter as your dose rate.
- Convert the full tank dose to ounces or tablespoons.
- Use the ratio line to mix by parts in a bucket.
- Note the grams of nitrogen the tank is carrying.
- Add product to part of the water, then top up.
- Check the strength call before you start spraying.
- Read the product note for handling quirks.
From Percent Nitrogen to Dose
One percent is ten thousand parts per million, so a five percent fish emulsion is a 50,000 ppm nitrogen stock. Dividing the stock by the target gives the ratio: 50,000 over 150 is one part product to 333 parts water. The same arithmetic in practical units is millilitres per liter, which is target ppm times one thousand over stock ppm, so 150 ppm needs 3.0 mL in every liter.
Because a liter of water weighs a kilogram, ppm here means one milligram per liter, and a 20 liter tank at 150 ppm is carrying three grams of elemental nitrogen. That number is the one worth remembering across products: two sprayers of the same nitrogen mass feed the same, whatever the bottle said. US conversions use 3.785 liters to the gallon and 29.57 millilitres to the fluid ounce.
Worked Example: Fish Emulsion at 150 ppm in a 20 Liter Tank
- Pick fish emulsion 5-1-1, a five percent nitrogen stock.
- Stock strength is therefore 50,000 ppm nitrogen.
- Target 150 ppm in the finished spray.
- Divide the two to get a ratio of one to 333.
- Per liter the dose is 3.0 mL, being 150 times 1000 over 50,000.
- The 20 liter tank needs 60.0 mL of product.
- That is 2.03 US fluid ounces in the bucket.
- Each gallon of spray carries 0.38 ounces.
- In tablespoons, a gallon takes 0.77 of the product.
- The tank delivers 3.0 g of elemental nitrogen.
- Fill water is 19.94 L once the product is counted in.
Typical Liquid Products and Where They Land
Label nitrogen, the strength most growers aim for, and the catch.
| Product | N percent | Usual ppm N | Catch |
|---|---|---|---|
| Fish emulsion | 5 | 150 to 200 | Odor, slow dry |
| Kelp extract | 0.1 | 10 to 20 | Hormone feed, not N |
| Worm casting tea | 0.5 | 40 to 60 | Brew and use same day |
| Aerated compost tea | 0.2 | not counted | Biology, not fertility |
| 20-20-20 soluble | 20 | 150 to 300 | Acidifies media |
| Urea stock | 46 | 100 to 200 | Needs warm soil bacteria |
| Bat guano tea | 3 | 100 to 150 | Clogs fine nozzles |
| Fresh urine | 0.7 | soil drench only | Far hotter than foliar |
Key Terms
- ppm nitrogen
- Parts per million, one milligram per liter of finished spray.
- Stock solution
- A concentrated mix measured out into the tank or system.
- Foliar feed
- Spray applied to leaf, usually at a much weaker strength than a drench.
- Soil drench
- Liquid applied to the media so roots do the feeding.
- Wettable
- A product that dissolves or disperses without leaving grit.
- Salt index
- How much a fertilizer raises media salinity and risks root burn.
Notes from People Who Mix a Lot of Tanks
- Commercial growers dose by grams of nitrogen per flat, not by the cap on the bottle, because bottle concentration and cap size both vary.
- Foliar feeding is mostly a micronutrient job. A foliar spray at a high nitrogen strength wastes product because the leaf absorbs far more than it can use and the rest sits on the surface.
- Aerated compost tea has no useful shelf life. Every hour after brewing the microbial count falls, which is why brewers say spray it within four hours or pour it on the compost.
- Weak and often beats strong and rare on the same crop, since a 60 ppm feed does not stall the plant's own nutrient uptake the way a 300 ppm drench can.
- Water pH matters as much as the dose for a foliar spray, because most nutrients are taken up far better when the solution is adjusted to around 6.0 to 6.5.
Common Mistakes & Fixes
- Reading the label ratio as a percent of the tank.
- Mixing to the strongest label rate for seedlings.
- Judging kelp by its nitrogen and overdosing the pot.
- Storing brewed compost tea for a week.
- Tank mixing tea with copper or strong alkaline products.
- Spraying in full sun with wet leaf that never dries.
- Guessing the dose with a bottle cap instead of a graduated cup.
- Assuming every brand of fish emulsion carries the same analysis.
- Spraying a strong mix onto wilted plants with closed stomata.
When to Reach for This
Use it when a bottle says a ratio and your sprayer is marked in liters, when a crop shows deficiency and you want a foliar correction that will not burn, when building a hydroponic stock, and whenever you compare a cheap strong feed with an expensive weak one. Pair it with the nutrient dose calculator for EC driven feeding, the fertilizer NPK calculator to see what the same dose contributes in bags, the ec ppm converter for solution strength, and the water pH adjustment calculator before you mix.
Compost Tea & Liquid Dilution Calculator: Frequently Asked Questions
What ppm nitrogen should I spray?
Around 40 to 60 ppm for seedlings and clones, 150 to 200 ppm for a growing crop in good light, and 300 ppm only for heavy field crops at full sun. Working upward is cheap while burning leaf tips costs you weeks. Strength can be raised as the plant gets bigger and the weather gets brighter.
How do I turn a 1-to-500 ratio into millilitres per litre?
Work from ppm rather than the ratio. Each millilitre per liter of a five percent product contributes 50 ppm nitrogen, so a 150 ppm target needs 3 mL in every liter, which is the one-to-333 the label implies. The calculator makes that division for whichever product you select.
Is compost tea a fertilizer?
Not in any dependable sense. Brewed tea carries a small amount of nitrogen and a lot of live microbes, and trials have shown its benefit comes mostly from biology and from the organic matter it adds, not from fertility. If you need growth, weigh and dose a real feed and treat tea as a soil condition.
Why does kelp need such a low dose?
Because it is only about a tenth of a percent nitrogen, so a normal 150 ppm target would demand more kelp than water. Kelp is applied at one to two millilitres per liter for its potassium, alginates and hormones, which land near 10 to 20 ppm nitrogen as a side effect.
Can I use the same mix for soil and for leaf?
You can, but leaf tissue is far more sensitive than a rooted soil drench, so most growers spray at half the strength they drench with. Roots can buffer a salt spike through the media; a young leaf cannot. When in doubt, dilute and add another pass.
Is diluted urine safe on food crops?
Applied to the soil of established crops at a strong dilution it is a long standing practice, but it is far hotter than any foliar mix, at roughly 7,000 ppm nitrogen undiluted. Keep it off leaf and off harvestable foliage, let it age only briefly if odor is a concern, and follow local guidance on use of human waste in gardens.
Sources & Further Reading
- Foliar Feeding of Crops — Michigan State University Extension. Foliar strengths, timing and why leaf uptake is limited.
- Compost Tea — Washington State University Extension. Evidence on microbial versus fertilizing value of brewed teas.
- Nutrient Solution Management for Greenhouse Crops — University of Florida IFAS Extension. ppm targets, stock solution mixing and pH interaction.
- Guide for the Use of the International System of Units — National Institute of Standards and Technology. Liter, gallon, fluid ounce and tablespoon conversions.
Chlorova Gardening Team
Builds, checks and documents every tool we publish
Chlorova editorial review
Checked against extension-service publications
Formula verified against published references · Updated
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