Calculate
Hydroponic EC and nutrient balance are related, but they are not the same measurement. EC indicates overall ionic conductivity; it does not identify the amount of each nutrient. University extension guidance explains why source-water composition matters. This article demonstrates one elemental mass-balance check, not a complete nutrient recipe, crop diagnosis or instruction to adjust acid or fertiliser blindly.
Record the inputs before calculating
Obtain source-water analysis including the relevant elements, EC, pH and alkalinity, and identify the crop and growth stage with a qualified adviser. Record final solution volume and the fertiliser’s elemental content basis. Labels may express phosphorus and potassium as oxides; do not substitute those percentages directly for elemental P and K. A TDS meter’s ppm conversion is not an elemental laboratory result.
Worked example and formula
Illustrative numbers only. Replace every assumed measurement, price, rate and performance factor with evidence for your situation. A 2026 review date does not turn an example into a current market quotation.
(100 − 20) mg/L × 100 L = 8,000 mg = 8 g N
8 g N / 0.20 = 40 g fertilizer
The hypothetical arithmetic assumes 100 litres final volume, a chosen target of 100 mg/L elemental nitrogen, and 20 mg/L nitrogen already in that source water. A fertiliser assumed to contain 20% elemental N supplies the remaining 8 grams of N in 40 grams of product. This is only a single-element illustration. It neither establishes a crop target nor balances the other elements supplied by that product.
Interpret the result correctly
Do not derive pH, EC, alkalinity or micronutrient adequacy from the NPK label alone. Water composition, product compatibility and other inputs can change the solution. Recheck measurements and product instructions rather than respond to a leaf symptom by adding more nutrient. Mixing concentrate components or dosing acids requires the appropriate manufacturer procedure; this guide supplies no such recipe.
Keep the original measurements, source date, units and assumptions beside the result. Change one assumption at a time to see its effect. A comparison is meaningful only when both options use the same scope. Do not silently combine different test procedures, products, dates or fee bases. Round a purchasing quantity upward only after completing the calculation; retain enough precision for intermediate steps.
Frequently asked questions
Which measurements should I use?
Use final volume, a water report and correctly interpreted elemental nutrient percentages, not just a TDS reading.
Is the example a guaranteed result?
No. Forty grams addresses one assumed nitrogen balance only and is not a complete or crop-specific feeding recommendation.
What should I check before acting?
Confirm water units, elemental-versus-oxide labels, crop needs and compatibility with an appropriate specialist.
Use the result and related tools
Use the nutrient tool only for the mass-balance assumptions it states. Keep measured pH/EC and the full nutrient programme separate. Read the existing calculator guide for its input definitions and limitations.
Sources and review scope
Reviewed 22 October 2026. The examples and arithmetic are original editorial illustrations, not field tests, certified designs, current price surveys or promised savings. Sources support the stated concepts; they do not certify these example inputs. The linked calculators have their own assumptions. These articles address specific decisions and complement the existing calculator guides. No Google search-volume or ranking claim is made.