How to use this Nutrient Mixing tool
Set your options in the calculator above, read the result, then verify with a calibrated meter when the decision matters. Bookmark this page for reservoir day — consistent units beat copying numbers from charts that never name their scale or bottle rate.
Formula reference
Amount (ml) = Reservoir volume (L) × Dosage (ml/L) for each nutrient part
Why accurate mixing matters more than brand loyalty
Hydroponic plants only access what you dissolve in the reservoir. Overdosing salt-based nutrients raises EC too quickly, burns root tips, and locks out calcium and magnesium even when those elements are present on the label. Underdosing starves fast-growing crops during peak vegetative growth and fruiting, which shows up as pale new leaves and stalled canopy development.
Most two-part and three-part formulas are designed so Part A and Part B stay separate until diluted. Mixing concentrates together can precipitate calcium phosphate and leave insoluble sludge that never reaches the plant. A calculator that scales each part to your exact reservoir volume removes guesswork and keeps the manufacturer’s ratio intact every refill.
How dosage rates relate to reservoir volume
Label rates are usually written as millilitres per litre or teaspoons per gallon. Those rates assume you are filling a known volume of water, not topping up blindly. If your reservoir holds 40 litres and the vegetative rate is 2 ml/L of Part A and 2 ml/L of Part B, you need 80 ml of each — not a rounded “splash” that drifts with every mix.
Always dose into the final fill volume you actually run. If you mix nutrients in a half-full tank and then top up with plain water, the EC will drop and your plants will receive less than the chart intended. Calculate for the working volume after topping up, then verify with an EC meter before returning the system to circulation.
Mixing order and water quality basics
Start with clean water at a stable temperature, ideally 18–22°C. Add Part A first, circulate until fully dissolved, then add Part B. Silica, calcium, and bloom boosters often have their own order — follow the brand’s sequence so you do not crash the solution with incompatible ions.
Tap water already contributes hardness and bicarbonate alkalinity. Soft or RO water may need a cal-mag base before standard doses, while hard water can push calcium higher than leafy greens prefer. Measure starting EC of your source water and subtract that background when interpreting target nutrient strength charts.
Checking strength after you mix
After mixing, stir thoroughly and wait a few minutes for temperature and ions to equalise, then read EC and convert to your meter’s PPM scale if needed. Target ranges differ by crop and stage — many leafy greens sit roughly 1.2–1.8 mS/cm in veg, while fruiting crops often run higher later in the cycle.
If EC is above target, dilute with pH-balanced water rather than adding more acid or base first. If EC is low, add proportional amounts of both nutrient parts rather than only one bottle. Recheck pH after every adjustment because nutrient salts and pH buffers interact; most hydroponic crops prefer roughly 5.5–6.5 depending on the system.
Frequently asked questions
Should I measure nutrients by volume or by weight?
Most hobby bottles are dosed by volume (ml/L). Commercial dry salts are often weighed for precision. Use the same method the manufacturer specifies, and keep measuring cups dedicated to nutrients so residue does not skew future mixes.
Can I mix a concentrated stock tank for later use?
Yes, but keep Part A and Part B in separate stock containers. Dilute into the reservoir at the calculated ratio when you fill. Never store a combined A+B concentrate — precipitation and nutrient lockout are common.
How often should I remake the reservoir?
Many recirculating growers change the reservoir every 7–14 days, or sooner if EC climbs from plant water uptake, if the solution smells off, or if roots look stressed. Top-ups with plain water between changes help, but they do not replace a full remake forever.
Related calculators
- EC ↔ PPM Converter — Convert between Electrical Conductivity (EC) and PPM across 500, 640, and 700 TDS scales.
- pH Adjustment Calculator — Estimate how much pH Up or pH Down solution is needed to reach your target pH.
- Reservoir Volume Calculator — Calculate the volume of your reservoir in litres or gallons based on container dimensions.
Keep learning
Pair this calculator with our pH & EC guide, crop targets in plant guides, and meter picks in product reviews.