Hydroponic Nutrient Mixing Calculator

How this is calculated

⛔ THIS TOOL DOES NOT TELL YOU WHAT STRENGTH TO FEED, AND NOTHING GENERIC SHOULD. Target EC or ppm depends on the crop, the cultivar, the growth stage, the light level, the temperature and the system - and the same plant wants different figures in propagation, in vegetative growth and in flower. Your nutrient manufacturer publishes a feed chart for their own product, and that chart is the authority here. What this page does is scale THEIR numbers to YOUR reservoir, which is arithmetic. ⚠️ NEVER MIX CONCENTRATES TOGETHER BEFORE THEY ARE DILUTED. This is the one operational rule worth putting above everything else, and every multi-part manufacturer states it. Concentrated parts react with each other - calcium from one part and sulphates or phosphates from another form compounds that drop out of solution - and the result is a precipitate on the bottom of the tank and a feed missing the very nutrients you paid for. Add each part to the FULL volume of water separately, stirring between additions. Never pour part A into part B. ⚠️ CHECK YOUR LABEL'S UNITS. Dose rates are quoted in ml per gallon and ml per litre, and a US gallon is 3.785411784 litres - so mistaking one for the other is a factor of nearly four in either direction. This tool works in ml per gallon and reports the same rate per litre so you can compare directly with a metric label. If the converted figure looks nothing like your bottle, you have entered the wrong unit. REDUCED STRENGTH IS A REAL PRACTICE AND IT IS AN INPUT. Seedlings, cuttings and stressed plants are commonly run at a fraction of full strength, and some growers run below label strength generally. What fraction is a judgement from your feed chart and your own observation, not something this page decides - it simply applies whatever percentage you enter. TOP-UPS ARE WHERE RESERVOIRS DRIFT. Plants take up water and nutrient at different rates, so a reservoir topped up with full-strength feed tends to climb in concentration while one topped up with plain water falls. Which you should use depends on your system and what your meter says - the tool gives you the figures for either, and a meter tells you which you needed. MEASURE, DO NOT ESTIMATE. Nutrient doses are small relative to reservoir volume, so a splash judged by eye is a large percentage error. A cheap syringe or measuring cylinder costs very little and removes the biggest source of variation between one mix and the next. pH IS ADJUSTED AFTER THE NUTRIENTS ARE IN, not before - adding them moves it. That is a separate step this tool does not cover.

Common questions

What EC or ppm should I run?

This tool will not tell you, and you should be wary of any generic source that does. Target strength depends on the crop, the cultivar, the growth stage, the light level, the temperature and the system - and the same plant wants different figures in propagation, in vegetative growth and in flower. Your nutrient manufacturer publishes a feed chart for their own product because the answer is specific to that formulation, and that chart is the authority. What this page contributes is scaling their numbers to your reservoir accurately, which is the part that is genuinely arithmetic.

Why can't I mix the concentrates together first?

Because they react. Concentrated parts are formulated to be kept apart until they are diluted - calcium in one part and sulphates or phosphates in another combine to form compounds that drop out of solution the moment they meet at full strength. What you get is a precipitate on the bottom of the tank and a feed that is missing exactly the nutrients you paid for, with no obvious warning beyond some cloudiness. Add each part to the FULL volume of water separately, stirring it in before the next goes near it. Never pour one concentrate into another.

My bottle is in ml per litre. What do I enter?

Multiply by 3.785411784 to get ml per gallon, since that is what this tool works in. Then check yourself against the per-litre output, which converts your entered rate back - if it does not match the bottle, the wrong unit went in. This matters because the two units differ by nearly a factor of four, and mistaking them is the single largest error available on this page. It is worth doing the check every time you change product, because manufacturers are not consistent about which unit they print.

Should I top up with feed or with plain water?

That depends on your system and on what your meter tells you, which is why the tool gives you the figures for either. Plants take up water and dissolved nutrient at different rates, so a reservoir topped up repeatedly with full-strength feed tends to climb in concentration, while one topped up with plain water falls. Neither drift is universal - it depends on the crop, the stage and the conditions. An EC meter costs little and turns this from a guess into a reading, and it is the single most useful instrument in a hydroponic setup.

What does running at reduced strength mean?

Feeding at a fraction of the label rate, which is common practice for seedlings, cuttings and stressed plants, and which some growers use generally. The tool applies whatever percentage you enter to every part equally, which keeps the ratio between them intact - that matters, because reducing one part and not the others changes the balance of the feed rather than its strength. What fraction to use is a judgement from your feed chart and from watching the plants, not something a calculator decides.

Do I need to measure precisely?

Yes, more than people expect. Nutrient doses are small relative to reservoir volume, so a splash judged by eye is a large percentage error - a few millilitres out on a dose of twenty is a tenth of your feed strength. A cheap syringe or a measuring cylinder costs very little and removes the biggest single source of variation between one mix and the next, which matters because you cannot diagnose a feeding problem if the feed is different every time. Measure the water volume properly too; a tank filled by eye is not the volume on the label.

When do I adjust pH?

After the nutrients are in, always. Adding concentrates moves pH, often substantially, so anything you do beforehand is undone by the mixing - adjust last, once everything is dissolved and stirred. That step is not covered by this tool, which handles quantities only. It is worth letting the solution settle for a few minutes and re-checking, since pH can drift as things fully dissolve, and worth re-checking again over the following days because it moves as plants feed.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Hydroponic Nutrient Mixing Calculator at https://www.bfcbrilliance.com/tools/hydroponic-nutrient-calculator.

What I entered:
- Reservoir volume (gal): ___
- Part A dose rate (ml/gal): ___
- Part B dose rate (ml/gal): ___
- Part C or additive dose rate (ml/gal): ___
- Strength you are running (%): ___
- Top-up volume (gal): ___

What it calculated:
- Part A for the reservoir: ___
- Part B for the reservoir: ___
- Part C or additive: ___
- Total concentrate going in: ___
- Part A for the top-up: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

More growing without soil tools