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Fertilizer Calculator

What would you like to do?

Choose a calculator mode based on what information you have.

Grams → PPM

Calculate what nutrient concentrations (PPM) you'll get from specific amounts of fertilizers.

Best for: You have fertilizers weighed out and want to know the resulting nutrient levels in your solution.

PPM → Grams

Enter your target PPM values and get the exact fertilizer amounts needed to achieve them.

Best for: You have specific PPM targets (e.g., from a recipe or plant requirements) and need to know how much of each fertilizer to use.

NPK Ratio → Grams

Enter nutrient ratios (like 3-1-2) and a target EC to get fertilizer amounts that match your desired balance.

Best for: You know the nutrient ratio you want (e.g., for a specific growth stage) and want to scale it to your desired EC/strength.
Step 2 of 2

How much solution are you making?

Enter the total volume of water you'll be mixing your fertilizers into.

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Step 3 of 3

How do you want to enter values?

Choose between commercial fertilizer notation or pure elemental values.

Step 4 of 4

What strength solution do you want?

Choose the EC (electrical conductivity) you want the mix to reach. It tells us how concentrated the nutrients should be, and we'll scale the fertilizer amounts to hit that strength for your batch.

Good starting point for most plants in active growth.

Step 3 of 3

Select Fertilizers & Enter Amounts

Check the fertilizers you're using and enter how many grams of each you'll add to your solution.

Step 4 of 5

Enter Target PPM Values

Enter the nutrient concentrations you want to achieve. At least one value is required.

Step 5 of 6

Enter Nutrient Ratios

Enter your desired nutrient ratios (e.g., N:P:K = 3:1:2). At least one must be greater than zero.

Step 5 of 5

Select Available Fertilizers

Choose the fertilizers you have on hand. The calculator will use only these to build your formula.

Step 6 of 6

Would you like to see a two-tank view?

Incompatible fertilizers detected in your selection

Your formula contains fertilizers that can react with each other when mixed at high concentrations (stock solutions). Specifically, calcium sources can precipitate when combined with sulfates, phosphates, or silicates at the wrong pH.

What is a Two-Tank System?

A two-tank system separates incompatible fertilizers into two concentrated stock solutions:

  • Tank A (Calcium): Contains calcium-based fertilizers like Calcium Nitrate
  • Tank B (Sulfates/Phosphates): Contains sulfate, phosphate, and silicate sources

Each tank is diluted separately, then combined in the final reservoir at working strength where the diluted concentrations are safe.

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Select Fertilizers and Enter Amounts

Target PPM Values

Enter your desired nutrient concentrations (at least one required). The calculator will find the best fertilizer combination to match your targets.

Oxide mode: Enter P₂O₅ and K₂O values (matches fertilizer labels and NPK Ratio to Grams output)
Elemental mode: Enter pure P and K values (scientific calculations)

Available Fertilizers

Select the fertilizers you have available. The calculator will use only these to build your formula.

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Target Nutrient Ratios

Enter your desired nutrient ratios (e.g., N:P:K = 3:1:2). At least one nutrient must be greater than zero. The calculator will find fertilizer amounts that match these ratios.

Oxide mode: Uses P₂O₅ and K₂O (standard fertilizer labels)
Elemental mode: Uses pure P and K (scientific calculations)

Select your target EC. Fertilizer amounts will be scaled to achieve this conductivity.
Ratios are preserved while adjusting overall concentration.

Select Fertilizers to Use

Choose which fertilizers you want to use. The calculator will find the best combination from your selection.
Priority: Lower values (1-10) = more preferred. The solver will try to use higher-priority fertilizers first.

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