Nutrient calculator help

Set your farm and, when possible, link the recipe to a grow cycle — that makes it easier to repeat a good feeding after harvest.

Steps

1. Water: enter source analysis (sodium, chloride, and alkalinity when you have them; EC and pH if available). A saved farm profile fills in automatically.
2. Feed systems: pick a manufacturer step or your own system — target ppm and, if set, step EC and pH apply.
3. Fertilizers: select the products you feed with.
4. Mix: on the website this is Magic wand; in the app it is the Recipes tab. Set the tank volume, one tank or an A/B layout, and if you want an EC cap and an ammonium share. You get up to five dose options.
5. Review the deviation table, EC estimate, and warnings. Save the recipe and optionally log feeding to the cycle journal.

On the website, the Recipes tab stores saved recipes: reload one into a calculation, repeat it in a new cycle, or duplicate it. In the app, the mix is calculated on the Recipes tab, and saved recipes sit on that same screen.

Label compositions and trust levels — on the Data sources page.

You set targets in mg/L and tick the fertilizers on your shelf. The calculator finds doses that pull the tank toward those targets without crossing the overdose ceilings. It tries first to assemble nitrogen, phosphorus, potassium, calcium and magnesium. Sulfur is counted, but it does not get to push calcium aside.

Label composition becomes tank contribution: oxide values on the pack (P₂O₅, K₂O, etc.) convert to elemental share; dose in g/L or mL/L becomes ppm.

Source water

What is already in water is subtracted from the target. If water exceeds your target for an element, you get a warning and the target is adjusted. Alkalinity can include acid neutralization — then added nitrogen or phosphorus enters the calculation.

How deviations are weighed

Each element's deviation is taken as a percent of its target and squared: a 20% shortfall weighs four times as much as 10%. So the app prefers several small deviations to one large one. Deviations are then added up with weights.

Here T is the target, A the achieved value, w the element weight, and k the overshoot multiplier (it equals one for a shortfall).

• Nitrate and ammonium nitrogen, phosphorus and potassium weigh 3. Calcium and magnesium weigh 2. Sulfur weighs 1, the same as micronutrients: it usually arrives with magnesium or potassium sulfate, and the calculator will not cut calcium to land sulfur exactly on target. Urea nitrogen weighs 2. Sodium and chloride, when you set a target for them, weigh 0.5 so they stay in view without outranking the nutrients.
• Overshoot costs more than shortfall: 1.25 times for macros, twice for micros. Excess micronutrients turn toxic sooner, and nothing can be taken back out of a tank.
• Elements without a target (boron and manganese from a micro mix when only iron is set, or sodium from a salt) cost nothing until they pass the top of their usual working range: B 0.5, Mn 1, Zn 0.5, Cu 0.1, Mo 0.05, Fe 2, Na and Cl 10 ppm. Above that level they are penalized.
• The sum is divided by the total weight of targeted elements, so an extra element cannot dilute the score.

Overdose limits and other constraints

• Each element has an upper overdose band vs target: NPK often up to +20%, Ca, Mg, and S up to +30%, micros up to +50%.
• The macro ceiling is hard: the calculator never crosses it. If the target cannot be reached without going over, you get a shortfall instead, and the card names which of nitrogen, phosphorus, potassium, calcium or magnesium stopped short of 90%.
• Micronutrients have two limits. The soft one is the larger of two values: target +50%, or the double dose at which those trials saw no leaf burn. The soft limit can be exceeded when the micronutrient comes as an impurity in a needed macro salt, or in a micro mix with a different element ratio. Above it the penalty grows faster and a yellow warning names the element. Example: the app will not cut P and K by 10% to avoid 0.01 ppm of copper from an NPK salt.
• The hard micro limit is the level at which, in the same trials, some plants showed toxicity or lost biomass (four times the usual dose). The app never exceeds it, even for the sake of other targets; if it had to cap a dose because of it, you get a warning. If you set a target above this level yourself, the app follows your target.
• Limits in ppm of the finished solution including water, soft and hard: Fe 8.04 and 16.08; Mn 1.98 and 3.96; Zn 0.4 and 0.8; Cu 0.38 and 0.76; B 0.98 and 1.96. There is no harm data for Mo, so only the soft limit applies: target +50%.
• Doses round to 0.001 g or mL per liter of working solution. Limits are checked on the rounded doses.
• You can set an EC cap, NH₄ share of total nitrogen, and a product dose cap when solubility limits apply. These limits are hard too.
• Same-brand A+B pairs dose in the manufacturer ratio (usually 1:1).

Where the micro limits come from: two cannabis trials in substrate where all micronutrients in the feed were given at single, double, and quadruple dose; the single dose is Fe 4.02, Mn 0.99, Zn 0.2, Cu 0.19, B 0.49 mg/L (HortScience, 2023, doi:10.21273/HORTSCI17162-23; Agrosystems, Geosciences & Environment, 2025, doi:10.1002/agg2.70044). The double dose caused no leaf burn. Biomass at that dose was not consistently lower, except for Sweetened at substrate pH 4.8. At the quadruple dose, lower-leaf burn showed up on only some plants: Sweetened at substrate pH 3.8, and Auto CBG grown without added silicon. Sweetened also lost biomass at the quadruple dose at every pH in the trial, including 6.5; Cherry Wine showed no clear biomass trend with dose. All micros were raised together, so these are tested levels of the mixture, not toxicity thresholds for each element.

EC estimate and other units

The EC estimate is guidance from composition. After mixing, still measure EC and pH with a meter. On the Elements tab you can view mmol/L and mg-eq/L — useful to compare with lab reports.

How far you can trust the result

The dose problem is solved exactly, without random search: for these weights and limits the program finds the best set of doses. The doses are then rounded to a 0.001 g/L step, and nearby rounding options are checked, so the result is practically as good as the exact solution. The same inputs always give the same doses.

• The same salts, the same water and the same target always give the same doses. The calculator does not cross an overdose ceiling to chase a prettier number.
• The same dose problem is also solved by a separate numerical program. On the recipes kept for that check, our result is not worse than that reference.
• Shown milligrams per liter are always recomputed from the doses on the card. A salt you ticked but the mix did not need stays at 0, so you can add some by hand.

What the calculation does not know: label accuracy (check the product's trust level), precipitation and binding in the tank, element availability at your pH, and plant uptake. The app counts how much of each element you add, not how much will be taken up. The weights and limits above are sensible defaults, not a law: if your crop has other priorities, compare options in the deviation table.

From the fertilizers you checked, the calculator builds the best mix, then tries a few genuinely different ones: it drops the main calcium, potassium, phosphorus or magnesium salt and solves again, and for a manufacturer's A+B pair it tries several label doses. You see up to five cards. It does not invent salts you did not tick.

• A mix needs a source of nitrogen, phosphorus, potassium, calcium and magnesium when those have a target. A missing sulfur salt does not throw the recipe out.
• Alternates often swap the main calcium, potassium, phosphorus, or magnesium product for another from your list.
• When an A+B pair is in the mix, both parts dose in the manufacturer ratio (usually 1:1); other salts fill the rest.
• The wand shows no dose below 0.01 g/L: such a line is either raised to 0.01 or removed, whichever lands closer to target. For micro mixes the floor is 0.001 g/L (1 mg/L), since they are dosed in milligrams.
• A product that barely improves the solution is dropped: a shorter recipe is easier to mix.
• Another card is shown only when nitrogen, phosphorus, potassium, calcium and magnesium are each at least 90% of target and none of them is above its overdose ceiling. Sulfur, high or low, does not hide a card. If no mix reaches 90% on all five, one card remains and names the short element. Often calcium is short because calcium nitrate also brings nitrogen, and nitrogen is already at its ceiling: then you need a calcium salt without nitrogen. The screen does not go blank.
• Very similar product sets merge so duplicates do not clutter the list.
• Shown ppm are always computed from the shown doses: there are no hidden additions. A salt you ticked but the mix did not need stays on the card at 0, so you can raise it by hand.

The percent averages, over the macros that have a target, how close each one landed. One hundred percent means every one of those macros is exact. Sulfur is in that average, so a high percent can still hide one short element among nitrogen, phosphorus, potassium, calcium and magnesium. Read the note on the card and the table, not only the number.

Cards are ordered like this: first the mixes where nitrogen, phosphorus, potassium, calcium and magnesium are all at least 90% of target; then a higher percent (the whole number you see); then fewer products; then a lower overall deviation, micronutrients included.

With several options, use Compare variants: rows are elements, columns are mixes. Green means under ten percent deviation, yellow ten to twenty, red twenty or more; + or − shows overshoot or undershoot. Pick the column that fits your priorities, then review that mix below.

For each element with a target you see target mg/L, achieved mg/L including water, and the difference in mg/L and percent. In tolerance for nitrogen, phosphorus, potassium, calcium and magnesium means at least 90% of target and not above that element's overdose ceiling (often +20% for NPK, +30% for calcium and magnesium). Sulfur on a standard profile uses a wider band, about 30% either side, and does not by itself throw the recipe out.

Yellow warnings also cover a missing liquid density, an over-strong stock, or ammonium above your cap. If nitrogen, phosphorus, potassium, calcium or magnesium did not reach 90%, the card still shows and names the short element. Read that line and the table before you mix.

The “Micronutrient above its soft limit” warning means the element came with a product the mix needs, and lowering it would pull the rest further from target. If that element is critical for your crop (copper or boron, for example), remove or replace the source product. The “Micronutrient at its hard limit” warning means the source product's dose was capped so the element stays below the level that caused harm in trials; other elements from that product may stay below target.

The same recipe on different water yields different tanks: well potassium and calcium reduce salt doses; sodium and chloride accumulate; bicarbonate alkalinity shifts pH and acid use.

• Enter at least sodium, chloride, and alkalinity — they feed the target calculation.
• Alkalinity can be bicarbonate (mg/L) or CaCO₃ equivalent — the calculator converts.
• Water pH and EC on the card are for your records; measure finished solution pH after mixing.
• Neutralizing alkalinity adds nitrogen (nitric acid) or phosphorus (phosphoric) — account for that in targets.

On the Elements tab: atomic weights, oxide-to-element conversion, and shares in selected products after label recalculation.

Even “pure” salts carry certificate impurities in practice (sodium in magnesium sulfate, chloride in calcium forms). Calculation uses declared percentages, not ideal stoichiometry.

A feed system is your week or stage steps: target ppm, EC, and pH. The active step feeds the wand target. Linking to a grow cycle keeps the plan with the crop; a feeding log writes to the farm event journal.

• After harvest, on Recipes you can repeat a recipe in a new cycle or copy the plan.
• A recipe tied to a feeding journal entry deletes only with confirmation.
• For yourself, keep recipe name, volume, doses, and measured EC and pH after mixing.

Each catalog product lists a data source and trust level: high, medium, low, or not yet verified. That shows whether you rely on official labels, manufacturer tables, or community references.

How the calculation itself is checked, and what it does not account for, is described under “How doses are calculated”. The same ppm target can be built with different salt sets — compare achieved ppm, not only grams per liter.

Full source list and update dates

Mixing order (working solution)

1. Fill the tank about three quarters with clean water.
2. Add part A (calcium forms), mix well.
3. Add part B (sulfates, phosphates), mix again.
4. Add micros and chelates if not already in A/B.
5. Top up to full volume.
6. Adjust pH last and measure EC of the finished solution.

In concentrate, calcium with sulfates or phosphates precipitates (gypsum, calcium phosphate), so A and B dilute in water separately. Do not mix A and B concentrates directly — water first. With A/B in the calculator, calcium does not share a concentrate with sulfates and phosphates: follow tank hints.

Chelates and precision

• Fe-EDTA usually holds iron to about pH 6.5; Fe-DTPA to about 7.5; Fe-EDDHA for more alkaline conditions.
• Doses round to 0.001 g/mL per liter; on large tanks scale to total volume and weigh to your scale precision.
• Follow SDS and concentrate storage rules.

Before feeding plants, measure EC and pH of the finished solution with calibrated meters and check against crop and growth stage.

• Why do doses differ from Hydroodo? One target can be met with different salts, and the programs split the compromise differently. We assemble nitrogen, phosphorus, potassium, calcium and magnesium to at least 90% of target when the salts on your shelf can do it, and we do not cross the overdose ceilings. Compare milligrams per liter, not only grams per liter.
• Why does the wand suggest a micro mix at 0.002 g/L? Micro mixes are concentrated and dosed in milligrams per liter. For a 100 L tank that is 0.2 g: weigh it on a jewelry scale or make a stock solution.
• Why two label calculation modes? Canonical (element) mode suits modern databases; the other mode compares to legacy tables if you still use them.
• Why does EC estimate differ from my meter? Temperature, organics, and impurities affect readings; measure after mixing.
• What if liquid density is missing on the label? The app warns and assumes 1.00 g/mL; enter density on the product card for precise milliliters.
• Does calculation work offline? Yes, after the catalog is on the device; saving a recipe to the farm needs network.
• How many options? At most five cards: one primary and up to four alternates. If none of them assembles nitrogen, phosphorus, potassium, calcium and magnesium to 90%, you still see one card, and it names the short element.