Crop: Hydroponic Calculator

Crop is a hydroponic nutrient calculator for greenhouse vegetable growers, leafy-greens hobbyists, herb gardeners, and microgreen producers. Every plant + stage target cites a primary source — Cornell CEA, Penn State Extension, UF/IFAS, or Produce Grower — so you can verify the published recipe behind every number.

WHAT'S INSIDE

• Plant + stage targets — lettuce (seedling + mature head), tomato (seedling, vegetative, fruiting), basil, leafy herbs (cilantro, parsley, mint, chives), cucumber, pepper, strawberry (fruiting), leafy greens (kale, chard, spinach, arugula), and microgreens. Lettuce, tomato, and herbs are the fully cited core; the rest is surfaced as broad guidance with explicit "per-stage tables are thinner for this crop" framing.

• Branded recipes — MasterBlend Tomato 4-18-38 (2:2:1 with calcium nitrate + Epsom), MasterBlend Lettuce 8-15-36 (the Cornell CEA leafy recipe), Jack's 3-2-1 (Jack's 5-12-26 + 15-0-0 calcium nitrate + Epsom), and the General Hydroponics Flora trio (Lite Feeding and Aggressive Leafy ratios).

• Twenty cited salts — calcium nitrate tetrahydrate, KNO₃, KH₂PO₄, K₂SO₄, MgSO₄·7H₂O, ammonium nitrate, monoammonium phosphate, magnesium nitrate, iron EDTA and DTPA, MnSO₄, ZnSO₄, CuSO₄, boric acid, sodium borate, sodium molybdate, calcium chloride, potassium chloride. Every percentage is derived from the chemical formula using IUPAC 2021 atomic weights.

• Target → salt-weight solver — the Resh / Mattson sequential satisfy textbook method. Enter your reservoir volume and a target ppm or pick a plant + stage, and Crop calculates the grams of each salt to mix.

• Reverse calculation — enter the salt weights you actually used and see the delivered ppm per element.

• Multi-reservoir EC + pH log — track a separate reservoir per crop or per zone, log readings over time, and surface drift warnings cited to the published source ("Per Cornell: lettuce mature 1.4–1.8 mS/cm; you logged 2.3 — dilute or top up plain water").

• Share-sheet mix sheet — export the day's reservoir target + salt weights + EC/pH range + named-source citation as plain text. Send it to yourself, paste it into your shop notebook, or print it.

• Unit flexibility — US gallons or liters, grams or ounces, EC scale 500 / 640 / 700 (matches Hanna, Bluelab, Cornell tables, or European meters).

DISCLAIMER

Crop presents Cornell CEA, Penn State Extension, UF/IFAS, and Produce Grower guidance for educational purposes. Verify recipes against current publications and your own meter readings before mixing at scale.

CITATIONS

Plant + stage recipes are sourced from Cornell CEA (Mattson & Lieth), Penn State Extension, UF/IFAS, and Produce Grower. Branded product analyses come from the manufacturer's published guaranteed-analysis labels and feeding charts. Method references are Resh, Hydroponic Food Production (7th edition), and Mattson & Lieth's hydroponic recipe calculation notes. Salt elemental percentages are derived from IUPAC 2021 atomic weights and CRC Handbook (100th edition) formula masses.

NO ACCOUNT. NO ADS. NO TRACKING. NO SUBSCRIPTIONS.

Crop does not collect any personal data. Everything stays on your device. One-time purchase, lifetime updates.