Target ppm in. Grams of each salt out.
Every hydroponic forum has the same thread: "how many grams of calcium nitrate for 100 litres". The answer depends on what else is in the mix, which is why a spreadsheet never quite works. This solves it properly.
WHAT IT DOES
- Solves grams of each salt for six elements at once (non-negative least squares, so it never asks for negative fertilizer)
- Ten common salts built in with label analyses: calcium nitrate, potassium nitrate, MKP, Epsom salt, potassium sulfate, magnesium nitrate, MAP, ammonium nitrate, calcium chloride, potassium chloride
- Eight crop presets: Hoagland, lettuce, herbs, tomato (vegetative and fruiting), peppers, cucumber, strawberry
- What you get versus target for every element, with the fix when the salts cannot make the ratio
- Ammonium share of nitrogen with a warning over 20%
- A and B stock tanks at any concentration, solubility-checked, with the millilitres to dose per litre of reservoir
- EC estimate, and a top-up calculator for when the reservoir has drifted strong or weak
- Litres or gallons
Who it's for
Anyone mixing from dry salts instead of buying bottles: Kratky jars, NFT lettuce, Dutch bucket tomatoes, grow tents.
What you get
- The calculator (one .html file, runs in any browser, offline)
- A 2-page quick-start guide
Good to know
- One file. No install, no account, no subscription, no internet needed after download.
- Your data stays on your computer. Export a backup any time; import it on another machine.
- Works on Mac, Windows, Linux and iPad (open the file in Safari or Chrome).
- Instant download.
What's inside the download
- Hydroponic-Nutrient-Calculator.html
- Quick-Start-Guide.pdf
Made by Matthew Busel, a one-person studio in Tuckahoe, NY. About me. Questions: support@tensorust.com.
Making and hobbies
Hydroponic Nutrient Calculator
grams of each salt for your target ppm, A/B stock tanks and EC
Pick the crop, tick the fertilizer salts you own, type the reservoir size. It solves the grams of each salt that lands N, P, K, Ca, Mg and S closest to target, splits them into A and B stock tanks that will not precipitate, checks solubility at your concentration, estimates EC, flags too much ammonium, and works out the top-up when the reservoir drifts.
Works or I fix it. If a file doesn't open or work as described, email support@tensorust.com within 30 days and I fix it or send a working copy. All sales are final, so check the screenshots or ask first.
- Updated
- Oct 2026
- File
- ZIP, 210 KB: 1 HTML app, 1 PDF
- Who it's for
- Anyone mixing from dry salts instead of buying bottles: Kratky jars, NFT lettuce, Dutch bucket tomatoes, grow tents.
One-time price in US dollars, checkout by Stripe. After paying you land on a page with your download link. Each link works for 15 minutes, and reopening that page makes fresh ones.
- Hydroponic-Nutrient-Calculator.zip