Can I use this calculator for soil growing?

You can use it to formulate liquid fertilizer for soil, but keep in mind that soil already contains nutrients. Start with a half-strength formula and adjust based on plant response and soil tests.

Why doesn't my recipe match the target exactly?

Each salt contributes multiple elements, so achieving exact targets for all elements simultaneously is mathematically constrained. The solver finds the closest possible match while keeping all salt amounts non-negative.

What is a good starting formula for beginners?

The Hoagland solution is the gold standard starting point. It has been used in plant science research since 1950 and provides a balanced nutrient profile for most plants. Start at half strength for seedlings.

Do I need all the micronutrients?

Yes, all micronutrients are essential for healthy plant growth. The amounts are tiny (measured in fractions of a ppm), but deficiencies cause serious problems. Iron deficiency is the most common.

How accurate are the teaspoon measurements?

Teaspoon measurements are approximations for convenience. For precise results (especially micronutrients under 5g), use a digital scale with 0.01g precision.

What if I don't have all the salts?

The calculator handles partial salt sets. It will show which target elements can't be met and suggest which salts to add.

How Nutrient Solution Calculator calculates its result

The solver treats the recipe as a system of linear equations, one row per target element and one column per available salt, then finds non-negative weights that come closest to the targets.

Contribution per gram: one gram of a salt that is X percent of an element, dissolved in V liters, contributes (X / 100) x (1000 / V) ppm of that element.
Target vector: each target is reduced by whatever the source water already supplies, and floored at zero.
Solve: a non-negative least squares routine finds the salt weights, so no salt can be assigned a negative amount. Exact hits on every element at once are not always possible, because each salt carries several elements.
Nitrogen form: when a nitrate to ammonium split is set, salts are weighted by how closely their own nitrogen form matches the requested ratio.
Accuracy grading: each element is marked exact within 5 percent of target, close within 15 percent, and off beyond that.
EC estimate: each element contributes ppm x (limiting molar conductivity / (atomic weight x 1000)), summed across the solution and reported in millisiemens per centimeter.
Scale conversion: PPM-500 is EC x 500 and PPM-700 is EC x 700.
Reverse mode: given salt weights, ppm = (grams / liters) x (percent element / 100) x 1000, summed per element and added to the source water.

Element concentrations are in parts per million (mg per liter). Salt weights are in grams, and grams per gallon. EC is in millisiemens per centimeter. Volume converts at 0.264172 gallons per liter.

Worked example

Running the calculator at its own default inputs: the full-strength Hoagland profile in a 5 gallon (18.93 liter) reservoir with the standard salt set:

Inputs

Macro targets: N 210, P 31, K 235, Ca 200, Mg 49, S 64 ppm
Micro targets: Fe 2.5, Mn 0.5, B 0.5, Zn 0.05, Cu 0.02, Mo 0.01 ppm
Salts offered: Calcium nitrate, potassium nitrate, monopotassium phosphate, magnesium sulfate, iron DTPA, manganese sulfate, zinc sulfate, boric acid, copper sulfate, sodium molybdate
Water: Reverse osmosis, contributing nothing

Result

Calcium nitrate: 22.3065 g (5.8928 g per gallon)
Potassium nitrate: 9.7065 g (2.5642 g per gallon)
Monopotassium phosphate: 2.5779 g (0.681 g per gallon)
Magnesium sulfate: 9.4059 g (2.4848 g per gallon)
Iron DTPA: 0.4302 g
Manganese sulfate: 0.0291 g (29.1 mg)
Boric acid: 0.0541 g (54.1 mg)
Zinc sulfate: 0.0042 g (4.2 mg)
Copper sulfate: 0.0015 g (1.5 mg)
Sodium molybdate: 0.0005 g (0.5 mg)
Resulting profile: N 210.8, P 31, K 237.45, Ca 200, Mg 49, S 64.98, Fe 2.5, Mn 0.5, Zn 0.05, B 0.5, Cu 0.02, Mo 0.01 ppm
Estimated EC: 2.29 millisiemens per centimeter
PPM-500 / PPM-700: 1,145 / 1,603
Total dissolved solids: 2.352 g per liter

Every target lands within 2 percent. Micronutrient doses this small call for a 0.01 g scale or a stock solution. The calculator also warns that calcium and sulfate sources should not share a concentrated stock tank, because calcium sulfate precipitates; use separate A and B tanks for concentrates.

Reference values

Hoagland solution, full strength, as stocked by the calculator
Element	Target (ppm)
Nitrogen (N)	210
Phosphorus (P)	31
Potassium (K)	235
Calcium (Ca)	200
Magnesium (Mg)	49
Sulfur (S)	64
Iron (Fe)	2.5
Manganese (Mn)	0.5
Boron (B)	0.5
Zinc (Zn)	0.05
Copper (Cu)	0.02
Molybdenum (Mo)	0.01

Accuracy grading applied to every element
Grade	Deviation from target
Exact	Within 5 percent
Close	Within 15 percent
Off	More than 15 percent

Measurement scales the calculator reports
Scale	Relationship to EC
EC	Direct meter reading, millisiemens per centimeter
PPM-500 (NaCl)	EC x 500
PPM-700 (KCl)	EC x 700
Total dissolved solids	Grams of salt per liter of solution

Nutrient Solution Calculator

Solves the salt weights needed to hit a target elemental nutrient profile in a given reservoir volume, and reverses a known recipe back into elemental concentrations with an estimated EC.