The calculator treats each target as ppm = mg/L of an element in your final solution. For each salt, the contribution is:
It builds a linear system for N, P, K, Ca, and Mg, then solves for the required grams per liter of each salt. If oxide basis is selected, P2O5 and K2O are converted to elements internally.
- Enter your total water volume and choose liters or gallons.
- Set your nutrient targets based on crop stage and system.
- Add any known source-water ppm to avoid overfeeding.
- Click calculate and weigh each salt carefully.
- If making stock, prepare Part A and Part B separately.
- Verify with an EC meter and adjust gradually.
| Use case | N (ppm) | P (ppm) | K (ppm) | Ca (ppm) | Mg (ppm) | EC indicator* |
|---|---|---|---|---|---|---|
| Leafy greens | 120 | 30 | 180 | 120 | 40 | ~0.98 |
| Herbs | 140 | 35 | 200 | 140 | 45 | ~1.12 |
| Fruiting crops | 170 | 45 | 240 | 160 | 55 | ~1.34 |
| Example calculation (20 L) | 150 | 40 | 200 | 150 | 50 | ~1.18 |
Nutrient targets and crop stages
Balanced recipes start with clear targets for nitrogen, phosphorus, potassium, calcium, and magnesium. Leafy crops often run well around N 100–160 ppm with moderate potassium, while fruiting crops shift to higher potassium and calcium for flowering, firmness, and transport. Use ppm goals as a specification, then adjust in small steps after observing growth rate, leaf color, internode length, and tip burn.
Source water impact and corrections
Water can contribute calcium and magnesium, especially in hard water. Entering water ppm lets the calculator subtract those contributions so your final mix stays on target. If a report lists P2O5 or K2O, the calculator converts them to elemental P and K internally for consistent comparisons. High bicarbonates can push pH upward, so record pH trends even when nutrient ppm looks correct.
Salt selection and compatibility
The calculator uses common salts and solves a linear system so each salt adds elemental ppm. Calcium nitrate is kept in Part A because it can form insoluble precipitates in concentrate with phosphates or sulfates. As a practical mixing rule, dissolve salts one-by-one, using warm water if needed, and never add dry fertilizer directly onto another dry fertilizer inside the container.
Stock concentrates for consistent dosing
Concentrates reduce weighing errors and speed mixing. A higher stock factor increases grams per liter in the stock, while the dose per liter decreases proportionally. Keep Part A and Part B in separate bottles, and avoid pushing solubility limits; if crystals form at room temperature, lower the stock factor or split salts across more volume. Label concentration, date, and intended dose rate on every container.
Verification, EC checks, and recordkeeping
An EC meter helps confirm consistency, but EC alone cannot identify individual ions. Use the EC indicator as a quick trend check and validate with plant response and reservoir top-up behavior. Measure pH (often 5.5–6.2), keep notes on temperature and light, and export CSV or PDF reports so you can repeat recipes and troubleshoot changes across seasons.
FAQs
1) What does ppm mean in this calculator?
ppm is mg/L of an element in the final solution. The calculator converts salt percentages into mg/L contributions and solves for grams per liter to match your targets.
2) Why does it split Part A and Part B?
Concentrated calcium nitrate can react with phosphates or sulfates and form solids. Separating parts helps keep stocks clear and reduces precipitation risk when mixing concentrates.
3) What if a salt result is negative?
Negative grams indicate the selected targets cannot be achieved with the chosen salts and analyses. Reduce conflicting targets, revise water contributions, or change salt options and label percentages.
4) Can I use gallons instead of liters?
Yes. Enter gallons and the calculator converts to liters internally. Results are still displayed as g/L and total grams, which keeps mixing accurate and easy to scale.
5) Is the EC value exact?
No. It is a simplified indicator based on summed target ppm and a selectable conversion factor. Use it for consistency checks, then confirm with a meter and plant performance.
6) How do I store stock solutions safely?
Use clean, opaque containers, label concentration and part, and keep away from heat. Shake gently before dosing if needed, and discard solutions that show persistent cloudiness or crystals.