Hydroponic Nutrient Calculator
This calculator turns a manufacturer dose written as mL per gallon into the exact amount of concentrate to pour into your reservoir. Type in your tank size in gallons or liters, the label dose, and how many bottles the line uses, and it returns the total mL and the mL to measure out per bottle. It is built for General Hydroponics, Advanced Nutrients, Masterblend and any brand that lists a per gallon rate.
How to dose a reservoir
- Enter your reservoir size in the left box and pick gallons or liters in the dropdown.
- Type the label dose into the Dose per gallon field, in mL/gal.
- Set Number of parts, such as 2 for a two bottle A and B set, or 1 for a single bottle.
- Read the Per part card for how much of each bottle to measure, and Total concentrate for the combined amount.
- Use Copy doses to save the reservoir volume, per part and total figures.
Examples
50 gallon tank, 5 mL/gal, A and B two part set
50 gallons, 5 mL/gal, 2 parts
189.27 L reservoir, 250 mL per part, 500 mL total concentrate
20 gallon tank, 8 mL/gal, a three part line
20 gallons, 8 mL/gal, 3 parts
75.71 L reservoir, 160 mL per part, 480 mL total concentrate
100 liter tank, 4 mL/gal, two part set
100 liters, 4 mL/gal, 2 parts
100 L reservoir, 105.67 mL per part, 211.34 mL total concentrate
Frequently asked questions
How is the nutrient amount calculated?
Each part is dosed at the label rate per gallon, so mL per part equals reservoir gallons times the dose per gallon. The total is that figure multiplied by the number of parts. Liters are converted to gallons first using 3.785412 liters per US gallon.
What does number of parts mean?
Many lines split their formula across several bottles, such as a two part A and B set or a three part grow, micro and bloom line, with each bottle added at the same per gallon rate. Set parts to 2 for A and B, or 3 for a three part line, and use 1 for a single bottle product.
Can I enter my reservoir in liters?
Yes. Choose liters in the unit dropdown and the tool converts to US gallons using 3.785412 liters per gallon before applying the per gallon dose. A 100 liter tank is treated as about 26.42 gallons.
My label lists a dose per liter, not per gallon. What do I do?
This field expects mL per gallon. To convert a per liter dose, multiply it by 3.785412 to get the equivalent per gallon figure, then enter that. For example 1.3 mL per liter is about 4.9 mL per gallon.
Should I add nutrients to a full or topped up tank?
Dose to the volume of water you are actually mixing fresh. If you top up between feeds, follow your brand guidance, since adding a full dose to only the fresh top up water can over concentrate the whole tank. Many growers top up with plain pH balanced water and only re dose on a full change.
Does the calculator adjust for grow stage or plant size?
No. It applies the single dose you enter evenly across the reservoir. Feeding schedules that ramp up through veg and bloom change the mL per gallon figure each week, so enter the rate for your current stage from the label or feed chart.
Should I check EC or PPM after mixing?
Yes. The result is a starting point from the label. Measure electrical conductivity or PPM after mixing and let it fully dissolve, then adjust toward the target range for your crop and stage. Young seedlings and sensitive plants usually want a lower strength than the full label rate.
Is this an exact feeding recommendation?
No. These are general guidelines based on your inputs. Always follow the label for your specific product, add parts in the order the maker states, and adjust using meter readings and how your plants respond over the following days.
Is my data private?
Yes. The whole calculation runs in your browser with no account and no upload, so your tank sizes and doses never leave your device.
Learn more
- How to mix A and B hydroponic nutrients without lockout
Why two and three part nutrients ship in separate bottles, how to add each part safely, and how per gallon dosing scales to any reservoir size.
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