Free tools
Grow Calculators
The numbers that separate a decent harvest from a great one. Every calculator here is free, works instantly in your browser, and explains the reasoning behind the result instead of just spitting out a figure.
VPD Calculator
Turn temperature and humidity into the one number that tells you what your plants actually feel. Stage-by-stage targets included.
Open calculator →PPFD & DLI Calculator
Find out whether your LED really covers your tent. Estimates PPFD and daily light integral from wattage and canopy size.
Open calculator →Nutrient & Feed Calculator
Target PPM and EC for every stage, adjusted for your source water, plus exactly how much solution to mix.
Open calculator →EC ⇄ PPM Converter
Convert across the 500, 640, and 700 meter scales. The mismatch between them is the top cause of accidental nutrient burn.
Open calculator →Harvest Date Calculator
Full timeline from the 15-hour dark soak through flip, harvest, dry, and cure — with a countdown to your harvest window.
Open calculator →Yield Estimator
Realistic dried-weight range in grams and ounces based on grams-per-watt benchmarks and your canopy training.
Open calculator →Watering Volume Calculator
How much water each plant needs per feed to hit 10-20% runoff, scaled to pot size and plant maturity.
Open calculator →Want the numbers checked against a photo?
Calculators tell you what the targets are. The AI Plant Doctor looks at your actual plants and tells you which target you are missing.