Hoe de berekening werkt
The chain is short and fully linear. Concentrate grams = dose mL × density, defaulting to 1.2 g/mL. Element ppm = grams × element fraction × 10⁶ ÷ tank millilitres, with a US gallon taken as 3.78541 litres. Because label NPK is stated as N, P₂O₅ and K₂O rather than pure elements, phosphorus is multiplied by 0.4364 and potassium by 0.8301 first. The dose is read as millilitres per gallon or per litre, not per tank.
Concentrate dose (mL) and Tank volume set the ratio, while the N, P and K percentage fields should be copied straight off the bottle — 6-2-4 is loaded by default. EC conversion factor changes nothing chemical; it only decides how the ppm total is expressed, offering 500 (NaCl scale, US), 640 (KCl scale, EU) and 700 (hydroponic). The same solution reading 1.2 mS/cm shows 600 ppm on the US scale and 840 on the hydroponic one.
The EC and total-dissolved figures only sum N, P and K. They ignore calcium, magnesium, sulphur, every micronutrient, the counter-ions those elements arrive attached to, and whatever your tap water already contains, so a real meter will read considerably higher than what appears here. Density also defaults to 1.2 g/mL for every product; check your own label, because thin liquid feeds sit nearer 1.0 and that error propagates into every ppm shown.
Veelgestelde vragen
Why does my EC meter read higher than the calculated EC? +
Because the estimate sums only N, P and K. Calcium, magnesium, sulphur, micronutrients, the counter-ions those elements arrive with, and the dissolved solids already present in your tap water all raise a real meter reading but are not counted here at all.
How do I turn P₂O₅ and K₂O on the label into actual P and K? +
Multiply the P figure by 0.4364 and the K figure by 0.8301, which the tool does automatically. A 6-2-4 label therefore delivers 0.87% elemental phosphorus and 3.32% elemental potassium, which is why the phosphorus row always looks smaller than the bottle suggests.
Should I pick the 500, 640 or 700 conversion factor? +
Match whatever your meter uses. US meters typically use the 500 NaCl scale, European ones the 640 KCl scale, and some hydroponic meters use 700. The choice does not alter nutrient concentrations at all — only the ppm number printed alongside the EC.
What do the ppm preset buttons actually set? +
They back-solve the concentrate dose so the tank reaches that figure as elemental nitrogen alone. Published grow-chart targets such as 800 ppm for heavy veg normally refer to total dissolved solids, a much larger quantity, so these presets ask for far more concentrate than a label would.
How much 6-2-4 concentrate goes into a one gallon tank? +
At the default 5 mL per gallon and 1.2 g/mL density that is 6 grams of concentrate, delivering roughly 95 ppm nitrogen. Halving the dose halves every ppm figure, since the whole chain is linear in dose, density and NPK percentage.
