Hydroponic Nutrient Solution Calculators: A Grower’s Guide
A hydroponic nutrient solution calculator helps you work out what your fertilizers actually deliver, not just how many grams or milliliters to add. For growers comparing nutrient programs, mixing individual salts, or preparing concentrated stocks, that makes the recipe easier to understand, repeat, and adjust.
At Custom Hydro, we use HydroBuddy and AlkCalc. We have also used CannaStats, SaltMix, PremixPPM, and the University of Pisa's Nutrient Solution Calculator. This guide explains where each fits, plus a newer option, Lost Art of Growing, for growers starting from an existing salt-based nutrient program.
Partnership disclosure: Custom Hydro has partnered with the creator of Lost Art of Growing, who participates as an affiliate in our affiliate program.
Which nutrient calculator fits your task?
- Build a recipe from elemental targets: Explore HydroBuddy.
- Work from an existing nutrient program toward a salt-based recipe: Explore Lost Art of Growing.
- Calculate the elemental profile of premixed fertilizers: Open the PremixPPM workbook.
- Evaluate contributions from individual compounds: Open the SaltMix workbook.
- Plan A/B nutrient stocks: Review the University of Pisa Nutrient Solution Calculator workbook.
- Calculate alkalinity treatment: Use AlkCalc alongside your nutrient formulation tool.
These tools do not all solve the same problem. A nutrient profiler adds up what a mix supplies. A formulation solver calculates fertilizer amounts to approach chosen targets. An alkalinity calculator addresses water treatment. None chooses the right crop targets or verifies the finished solution for you.
HydroBuddy: formulate from nutrient targets
HydroBuddy, developed by Daniel Fernandez, is a free, open-source nutrient formulation program. Its documented features include calculating fertilizer weights from elemental targets, calculating nutrient concentrations from fertilizer weights, custom fertilizer analyses, source-water inputs, and direct-addition or A/B concentrate calculations.
Its value is seeing the recipe as a whole. Potassium nitrate supplies potassium and nitrogen. Calcium nitrate supplies calcium and nitrogen. Monopotassium phosphate supplies phosphorus and potassium. Adjusting one fertilizer therefore changes more than one nutrient.
Review the calculated profile after each revision. A solver may find the closest available fit from your selected materials without meeting every target exactly. Verify database entries against the exact fertilizer grade you buy, and consult the developer's HydroBuddy tutorials and documentation for your version.
Lost Art of Growing: start with a nutrient program you know
If you want to explore individual fertilizer salts without beginning with a blank set of elemental targets, Lost Art of Growing is worth evaluating. Its Nutrient Replication Calculator uses entered guaranteed-analysis percentages and dosage rates to estimate a salt-based recipe, with outputs for batch tanks, stock tanks, or dosers.
The service provides a shopping list of inputs. Paid Grower Access also includes a Feeding Scheduler for planning usage rates through the growing cycle. That gives growers a practical workflow: examine an existing program's elemental profile, review the inputs, then check how the proposed recipe fits their mixing system.
Try the calculator before subscribing
As listed on October 24, 2026, the seven-day calculator trial requires no credit card and does not charge automatically when it ends. It lets you run a replication and view the ppm breakdown, but excludes the Feeding Scheduler, saving formulations or regimens, and usage-rate features.
Custom Hydro purchase-linked discount
Lost Art of Growing offers an access discount tied to confirmed purchases through its Custom Hydro links. Under the terms listed on October 24, 2026, a qualifying purchase reduces the next monthly renewal from $50 to $45 and opens a 30-day window to switch to annual access for $475 instead of $500. After that window, standard pricing resumes unless another confirmed qualifying purchase opens a new window. The one-time $50 month is not discounted.
Use the Custom Hydro links provided by Lost Art of Growing for qualifying purchases; do not assume an unrelated order triggers the benefit. Explore the trial, current plans, and Custom Hydro discount conditions before signing up.
Matching a declared nutrient analysis does not establish that two products are chemically identical or will produce identical crop performance. The developer describes its output as a practical recipe estimate, not a certified analysis or a guarantee of matching EC. Verify the inputs and test a small batch before scaling up.
CannaStats, PremixPPM, and SaltMix: profile an existing mix
The legacy CannaStats download page lists PremixPPM and SaltMix. The shared workbooks linked above provide another way to inspect these resources.
PremixPPM supports up to seven fertilizer analyses and combines their contributions with source-water nutrients and other adjustments. Its instructions also address liquid-fertilizer density and mix-cost calculations. SaltMix performs nutrient-content calculations for individual compounds and includes purity inputs and conversion factors.
Use PremixPPM to examine a multi-product feeding program and SaltMix to evaluate contributions from individual salts. Check old product entries against current labels, confirm spreadsheet compatibility, and verify a known calculation before relying on a legacy workbook for production mixing. Being able to view a workbook online does not prove every original control or calculation functions as intended.
University of Pisa Nutrient Solution Calculator: plan A/B stocks
We have also used the workbook developed by Dr. Luca Incrocci at the University of Pisa, Italy. Its Quick Start Guide credits Luca Incrocci and acknowledges the EUPHOROS research project.
The publisher's resource page describes calculations for A/B stock composition and cost using crop recipes, irrigation-water ion composition, stock-tank volumes, and dilution ratio. It also assesses possible precipitation from excessive stock concentration.
Before using a stock recipe, confirm the software requirements and whether each output describes the concentrate or final irrigation solution. A correct nutrient total does not by itself establish stock compatibility.
AlkCalc: include water treatment in the nutrient budget
AlkCalc addresses irrigation-water alkalinity treatment. Alkalinity and pH are different measurements: two sources with similar pH can require different acid amounts because their acid-neutralizing capacity differs.
Enter your laboratory's alkalinity units correctly. A value reported as ppm calcium carbonate cannot simply be entered as bicarbonate concentration or milliequivalents per liter without conversion. Use the correct acid concentration as well.
AlkCalc calculates acid requirements and associated nutrient contributions. Those nutrients belong in the final recipe: nitric acid contributes nitrogen, phosphoric acid contributes phosphorus, and sulfuric acid contributes sulfur. Follow the product label, safety data sheet, and equipment requirements, and have treatment settings verified by appropriately trained personnel.
How to calculate fertilizer ppm: a worked example
For dilute nutrient solutions, elemental ppm is approximately milligrams per liter (mg/L). If a fertilizer contains 19% elemental calcium and you want it to add 100 ppm calcium to a final volume of 1,000 liters:
Fertilizer grams = added nutrient ppm × final liters ÷ (elemental nutrient fraction × 1,000)
100 × 1,000 ÷ (0.19 × 1,000) = approximately 526 grams.
If that fertilizer also contains 15.5% nitrogen, this dose adds approximately 81.6 ppm nitrogen. Include that contribution before adding another nitrogen source. This is a calculation example, not a complete crop recipe.
Conventional fertilizer grades express phosphorus as P₂O₅ and potassium as K₂O. If your calculator requires elemental values, multiply P₂O₅ by approximately 0.4365 to obtain P, and K₂O by approximately 0.8301 to obtain K. Do not convert twice if the tool already handles these inputs.
Before you mix a production batch
- Start with water data. Account for nutrients already present. Subtract the source-water contribution from the intended final target for each nutrient; if the source already exceeds a target, fertilizer additions cannot remove that excess.
- Verify the fertilizer entry. Use the exact analysis, chemical form, and relevant purity information. For liquids, check whether the calculation requires density.
- Check units and dilution. Confirm liters versus US gallons, grams versus milliliters, and final solution versus stock concentration. Verify the injector's ratio definition.
- Check compatibility. Keep concentrated calcium separate from incompatible concentrated phosphate and sulfate sources. Review solubility, stock strength, and mixing instructions.
- Test and record. Prepare a small batch, inspect for precipitation, measure EC and pH with calibrated instruments, and record the water source, fertilizer grades, quantities, and injector settings.
Common grower questions
Does an on-target EC mean the nutrients are balanced?
No. EC indicates overall dissolved-ion conductivity, not the concentration of each element. An acceptable reading can still accompany an unbalanced recipe.
Is calculated nutrient ppm the same as a meter's ppm reading?
No. Elemental ppm describes an individual nutrient concentration. A typical conductivity-based ppm meter estimates total dissolved solids using a conversion factor. Do not expect the two values to match directly.
Can I scale a reservoir recipe straight into a stock tank?
Not without checking dilution and compatibility. Fertilizers that coexist at final irrigation strength may precipitate when concentrated. Review the stock formulation and equipment settings separately.
Choose a tool, then verify the recipe
Use HydroBuddy when you want to work from elemental targets, a profiler when you want to understand an existing mix, and AlkCalc when water alkalinity needs treatment. If you want to explore a salt-based version of a program you already know, review Lost Art of Growing's trial and access options.
The goal is not more decimal places. It is a nutrient program you can understand, reproduce, and adjust with purpose.
