Hydroponics
Nutrient solution calculator
Reservoir volume and your own product’s dilution into millilitres of each part — for a full change or a top-up. It applies the figure on your bottle and has no view on what that figure should be.
The question this answers: “The bottle says 2ml per litre. My tank is 24 litres and I am only changing half of it. How much of each part goes in?”
Result
- Mixing
- 20 litres
- A full reservoir.
- Part A
- 40 ml
- Part B
- 40 ml
- Part C
- 0 ml
- Total concentrate
- 80 ml
- Add each part to the water separately and stir between them. Concentrates poured together undiluted can react and drop nutrients out of solution.
Show the working
- Volume being mixed
min(20 l asked for, 20 l reservoir)20 l - Part A
2 ml/l × 20 l40 ml - Part B
2 ml/l × 20 l40 ml - Part C
0 ml/l × 20 l0 ml
Mixing: 20 litres. Part A: 40 ml. Part B: 40 ml. Part C: 0 ml. Total concentrate: 80 ml
Millilitres per litre times the number of litres being mixed, for each part separately. Where the volume asked for exceeds the reservoir it is capped at the reservoir, because mixing more than the tank holds is nearly always a slip rather than an intention.
- That the dilution on your label is quoted per litre. Several lines quote per gallon, and some quote a range across the growth stages rather than a single figure — the tool applies whatever you type and cannot tell the difference.
- That the parts are added separately to water. Concentrates poured together undiluted can react and drop nutrients out of solution, which is why the total is reported alongside the parts rather than instead of them.
- That your reservoir figure is the water volume rather than the container’s nominal size. Media, net pots and a plant displace a real fraction of a small tank.
- It publishes no strength, no target and no feeding schedule. What concentration a crop wants depends on the product, the growth stage and what is already dissolved in your tap water, which varies enormously across Britain — the correct figures are on the bottle you bought.
- It does not adjust for what is already in the reservoir. A top-up dilutes into a solution that has already drifted, which is the argument for a full change on a schedule rather than a reason to compute a correction.
- Nothing here is about pH. Adjusting pH after mixing is a separate step and a separate measurement.
Runs entirely in your browser — nothing you type is sent anywhere. Last reviewed 2026-08-19. More on Hydroponics.