Calcium PPM Calculator
Blossom end rot on tomatoes, tip burn on lettuce — classic calcium problems, and they happen even when calcium is "in the mix" because uptake depends on the actual PPM. Target 100–200 PPM and measure it.
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Calcium PPM Calculator
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Blossom end rot on tomatoes, tip burn on lettuce — classic calcium problems, and they happen even when calcium is "in the mix" because uptake depends on the actual PPM. Target 100–200 PPM and measure it.
How to use this calculator
- Enter volume.
- Enter target Ca PPM.
- Enter fertilizer Ca%.
- Get grams.
The formula
Grams = target PPM × liters ÷ 1,000 ÷ Ca fraction.
What the inputs mean
The target is the concentration you want, in PPM. The volume is how much liquid you are treating. The calcium content (%) corrects for product strength, because most products are not 100% active ingredient. The result tells you exactly how much calcium fertilizer to add.
Worked example
100 L, 150 PPM Ca, calcium nitrate at 19% Ca: 150 × 100 ÷ 1,000 ÷ 0.19 ≈ 79 g.
Quick reference
| Crop | Target Ca PPM |
|---|---|
| Lettuce | 100–150 |
| Tomato | 150–200 |
| Pepper | 150–200 |
Keep Ca separate from sulfate/phosphate concentrates.
Where you will actually use this
Calcium cannot be remobilized in the plant — new growth needs a constant supply.
- Tomato/pepper production
- Lettuce tip-burn prevention
- Hydroponic calcium management
Mistakes that give wrong answers
- Mixing calcium nitrate with sulfates/phosphates in concentrate (precipitates)
- Low transpiration reducing uptake
Key takeaways
- Formula: Ca fertilizer (g) = Target Ca PPM × Volume (L) ÷ 1,000 ÷ Ca fraction
- Remember: Keep Ca separate from sulfate/phosphate concentrates.
- Watch out for: Mixing calcium nitrate with sulfates/phosphates in concentrate (precipitates)
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
What calcium PPM for hydroponics?
100–200 PPM.
Why do my tomatoes get blossom end rot?
Usually calcium uptake issues — check PPM, pH, and watering consistency.