Plant Care
- • Climate Control & VPD16
- • Disease & Pest Management14
- • Nutrient Solutions & EC34
- • Plant Health Monitoring7
Inputs
6 parameters · live recalculation on every change
L
1L
200L default
5000L
MS/CM
0.2mS/cm
1.8mS/cm default
3mS/cm
Advanced Settings — Deterministic Corrections
PPM
0ppm
50ppm default
800ppm
Insight band · live
Six ions to total feed
The finished feed is exactly these six ions added together — no hidden salt, no silent buffer.
- Nitrogen 101.99 101.99 ppm
- + Phosphorus 29.39 131.38 ppm
- + Potassium 121.00 252.38 ppm
- + Calcium 70.87 323.25 ppm
- + Magnesium 21.61 344.86 ppm
- + Sulphur 28.52 373.38 ppm
- Total feed PPM 373.38 373.38 ppm
Solution EC: 1.80 mS/cm
Cost / L: 1.27 ¢/L
Running total after each term — the final net matches the headline reading in the result card, kept in sync live.
Deterministic model
6 inputs · 10 outputs
Runs 100% in your browser
This is a deterministic model: the same inputs always produce the same outputs, calculated entirely in your browser with nothing sent to any server. It is a planning aid — not a quote, not a dosing instruction, and not a yield forecast. Treat every line as a working estimate and validate it against your own prices and measurements.
It models one system: The elemental PPM formulator. Feed in reservoir volume, target EC and source-water PPM and it returns the real NPK, Ca, Mg and S in parts per million — scaled across Masterblend, two-part A/B, one-part and DIY dry-salt builds, with dilution stepper, top-up and silica dosing built in.
What the Nutrient Lab Pro — Elemental PPM Formulator returns
The engine computes 10 outputs from your 6 inputs. The headline number is Total Feed PPM (ppm), alongside Nitrogen (N), Phosphorus (P), Potassium (K). Every output updates live as you change a parameter.
What it does not do
Outputs depend on the inputs and assumptions shown here. Confirm relevant measurements and local conditions before acting.
STEP 01
Set Reservoir Volume and Target EC
Measure your reservoir in litres and choose the target electrical conductivity for the current growth stage. Veg runs 1.2–2.0 mS/cm, flower 1.8–2.6 mS/cm, clones stay lower for safety.
STEP 02
Enter Source Water PPM Baseline
Input your tap or RO water PPM on the 500 scale. The engine subtracts this baseline from total dissolved solids so fertiliser is not double-counted.
STEP 03
Choose the Formula Profile Family
Select Masterblend 4-18-38, two-part A/B, one-part crystal, or DIY dry salts. Each profile uses its guaranteed analysis ratios to split nutrients.
STEP 04
Compute Total Feed and Fertiliser Portion
Total feed equals EC times 700. Subtract source PPM to obtain the true fertiliser portion available for elemental distribution across the tank.
STEP 05
Distribute Elements by Profile Coefficients
Multiply the fertiliser portion by each element coefficient for N, P, K, Ca, Mg and S. Scaling stays linear with EC for predictable transitions.
STEP 06
Apply Additives and Check Costs
Add silica for extra potassium or CalMag for calcium and magnesium, then read cost per litre and batch cost. Verify EC against the lockout ceiling.
\text{TDS} = \text{EC (mS/cm)} \times 700
Total dissolved solids from solution EC — 700 scale
\text{PPM}_{fert} = \max\!\left(0,\; \text{EC} \times 700 - \text{PPM}_{source}\right)
Fertiliser portion after subtracting the source-water baseline
\text{N}_{ppm} = k_{N} \times \text{EC}
Elemental nitrogen from the formula-profile coefficient
e_{i} = k_{i} \times \text{EC} \quad (i \in \{P, K, Ca, Mg, S\})
General elemental split — each profile scales linearly with EC
m_{g} = 2.4\;\tfrac{\text{g}}{\text{gal}} \times \frac{\text{EC}}{2.0\;\text{mS/cm}}
Masterblend 4-18-38 dry-salt scaling from the 2.0 mS reference batch
\$\cdot\text{L}^{-1} = \frac{\text{g}/\text{L} \times \$\/\text{kg}}{1000}
Nutrient cost per litre from dry-salt dose and product price
Elemental ppm are estimates driven by each formula family\u2019s guaranteed-analysis ratios, scaled to your target EC — not a lab assay, but within 5–10% for dose planning.
The 700 scale is the industry EC conversion used across most grower meters; switching meters changes the TDS figure, not the real elemental content.
Silica (K₂SiO₃) always goes into the reservoir first, before base nutrients, to avoid precipitation; the engine adds ~2 ppm K for it.
At EC above the stage ceiling plus 0.4 mS/cm the engine flags a salt lockout risk — raise EC slowly, never in a single shift.
- Blok, J. (2015). Nutrient Solutions in Hydroponics. Practical Hydroponics & Greenhouses.
- Masterblend 4-18-38 guaranteed analysis — N-P-K 4-18-38, Ca 18, Mg 6 (tonnage basis).
This model combines the earlier Hydroponic-nutrient-calculator, Nutrient-calculator, Ab-dosing, Masterblend-calculator, Dilution-stepper, Top-up-dilution, Silica-dosing, Diy-hydroponic-nutrient-formulation models.
Q1: How accurate are the elemental PPM numbers? ▾
Each formula profile is built from the guaranteed analysis ratios its manufacturers publish, scaled linearly with conductivity. That gives dose-level accuracy within about 5–10% of a lab ICP assay — more than enough to plan feeds, compare formulas and diagnose lockout. It is a planning tool, not a substitute for periodic lab testing.
Q2: Why do I need to subtract source water PPM? ▾
Your tap or well water already carries dissolved minerals, so hitting a target EC with fertiliser alone overshoots the real feed. Entering the source baseline lets the engine compute the true fertiliser portion — on hard water this routinely cuts the recommended dose by 10–20%.
Q3: What EC should I run for each growth stage? ▾
Clones and seedlings stay light at 0.6–1.0 mS/cm, vegetative growth runs 1.2–2.0 mS/cm, and flower builds 1.8–2.6 mS/cm. The engine colours the EC gauge against your selected stage and flags lockout when you push more than 0.4 mS/cm above the ceiling.
Q4: Which formula profile is best for me? ▾
Masterblend 4-18-38 is the proven, cheap and consistent workhorse — start there. Two-part A/B formulas give finer P/K control through flower, one-part crystals are the most foolproof, and DIY dry salts are the cheapest once you trust your scales. The engine keeps the same elemental output across all of them so comparisons are apples-to-apples.