Hydroponics pays. The chemistry is what kills it.
A spare tent and a couple of reservoirs can out-produce a backyard plot several times over; that's how hydroponics pays: basil sold to restaurants, strawberries in a garage through winter, lettuce turning over every three weeks. Then the plants yellow, curl, and stall, and the water chemistry that kills them never shows up on the bottle label.
The label assumes distilled water; yours already has calcium and alkalinity in it. It never warns you that calcium and sulfate in one stock tank turn expensive nutrients into sludge, or that iron quietly stops working above pH 6.5. None of this is hard. It's just invisible, until something dies.
Hydroponicity is the hydroponics nutrient calculator built for side-hustle growers. Tell it your water, your salts, and what you're growing, and it solves the exact grams of each fertilizer, corrected for your tap, checked for precipitation, matched to your pH. You get a number you can trust and the reason it's right.
No account needed for the free calculators. The engine keeps the full math intact. The surface just hides what you don't need day to day.
Start with a calculator
Each tool solves one real problem and lives at its own URL. No sign-up to try them.
EC ↔ ppm converter
Convert between EC and ppm on any meter scale (500 / 640 / 700), with 25 °C temperature correction.
Targets “ec to ppm hydroponics”
Fertilizer label decoder
Turn a guaranteed-analysis N-P-K label (oxide form) into the elemental percentages every ppm calc needs.
Targets “convert P2O5 to P”
Recipe solver
The real multi-salt engine: enter target ppm, get grams per fertilizer and a solved ion balance. One free solve.
Targets “hydroponic nutrient calculator”
Dilution & injector calculator
Solve C₁V₁ = C₂V₂ for any missing value, and size stock concentrate for a 1:R injector, with the ratio convention made explicit.
Targets “nutrient dilution calculator”
VPD calculator
Air temp, humidity, and leaf-temperature offset → air and leaf VPD in kPa, checked against stage targets.
Targets “vpd calculator”
Dehumidifier sizing
Pints-per-day capacity for a grow room (from water fed) or a drying room (from wet harvest weight).
Targets “grow room dehumidifier size”
Humidifier sizing
Moisture output needed to hold a target RH against air exchange, from room volume and current conditions.
Targets “grow room humidifier size”
AC / BTU sizing
Turn light and equipment wattage into the BTU/hr and tonnage of cooling the room actually needs.
Targets “grow room BTU calculator”
Exhaust fan & carbon filter CFM
Room volume and exchange rate → base CFM, derated for carbon filter and ducting so the fan you buy keeps up.
Targets “grow tent fan size calculator”
CO₂ enrichment calculator
Grams of CO₂ to reach a target ppm, ongoing loss to air exchange, and time-to-setpoint for your injector.
Targets “grow room co2 calculator”
Grow light coverage & PPFD
Fixture wattage and efficacy over a coverage area → average PPFD and DLI, checked against stage targets.
Targets “ppfd calculator”
Pump & irrigation flow rate
Reservoir turnover and emitter demand → the GPH rating to shop for, with head height accounted.
Targets “hydroponic pump size calculator”
Electricity cost calculator
Add up lights, fans, and pumps by wattage and hours → daily, monthly, and per-cycle running cost.
Targets “grow light electricity cost”
Yield estimator & production planner
Growth rate, area, and cycle length → predicted yield, cycles per year, annual output, and revenue.
Targets “hydroponic yield calculator”
Research-grade math, an operator-friendly surface
Multi-salt recipe engine
Not a stack of single-salt calculators: a constrained weighted least-squares solve across every fertilizer at once, so one salt's contribution to K doesn't wreck your Mg.
Reservoir & system tracking
Every system carries its own state: active recipe, water source, last reading. Log an EC/pH reading and it's compared against that system's target automatically.
Advanced, yet simple
The full engine (source-water correction, ion balance, EC estimate, pH dosing) stays intact underneath. The UI exposes only what a side-hustle grower uses day to day.
The engine shows its work
A missed EC or pH warning is a real dosing error, so safety warnings and approximation caveats are always free and always visible, regardless of tier. Every result traces back to its inputs, so you can verify the math before you weigh anything out.
- Safety warnings never sit behind a paywall
- A collapsible provenance trace on every result
- Units shown next to every number: no unit hidden in a tooltip
Keep calcium and sulfate in separate stock tanks: they precipitate as gypsum when concentrated.
Gated by where you are, not how hard the math is
Free
Acquisition hooks: the commodity converters, plus one real solve.
- EC ↔ ppm / TDS converter (all meter scales)
- Fertilizer label decoder (oxide → elemental)
- One recipe solve: no save, export, or re-run
- All safety warnings & caveats (always free)
Funnel position, not math complexity.
Start freePro
Most completeThe full multi-salt recipe solver bundle, with persistence.
- Multi-salt recipe solver (weighted least-squares)
- Source-water correction + RO blend guidance
- Cation–anion ion balance + EC estimate
- Integrated pH / acid dosing
- Save, export & re-run recipes across systems
The paid conversion moment.
Go ProReservoir add-on
Reservoir management & stock-injector scaling for recirculating setups.
- Stock A/B batch sizing with compatibility rules
- Injector / proportioner ratio (convention-aware)
- Accumulation tracking (Na, Cl) + dump scheduling
- Reservoir refresh-fraction planning
Subscription if you recirculate; otherwise a one-time unlock.
Add to Pro