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EC And TDS For Hydroponics Calculator

Work out ec and tds for hydroponics instantly with clear inputs, formula shown and shareable results.

About EC And TDS For Hydroponics Calculator

TDS meters do not measure dissolved solids; they measure conductivity and multiply by a scale factor. The three common scales — 500, 640 and 700 ppm per mS/cm — give readings up to 40% apart for the same solution, which is why EC in mS/cm is the safer unit to specify a recipe in.

Formulas

EC to TDS

TDS (ppm) = EC (mS/cm) x scale factor (500, 640 or 700)

Dilution

Water to add = volume x (EC now - EC target) / EC target

Worked example

With the default values below, EC And TDS For Hydroponics Calculator returns Total Dissolved Solids of 1,000.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Electrical Conductivityminimum 0.01 mS/cm
2 mS/cm
TDS Conversion Factorone of 500 scale (NaCl / ppm500), 640 scale (ppm640), 700 scale (KCl / ppm700)
500 scale (NaCl / ppm500)
Target EC For The Cropminimum 0.01 mS/cm
2.4 mS/cm
Tank Volumeminimum 0.1 L
500 L

Results

Total Dissolved Solids
1,000.0
Target TDS
1,200.0
EC Gap To Target
0.400
Dilution Water If Over Target
0.00

Step by step

  1. 1Values used
  2. 2EC to TDS
  3. 3Dilution
  4. 4Total Dissolved Solids= 1,000.0
  5. 5Target TDS= 1,200.0
  6. 6EC Gap To Target= 0.400
  7. 7Dilution Water If Over Target= 0.00

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What EC do common crops want?

Lettuce and leafy greens 1.2-1.8 mS/cm, tomato and pepper 2.2-3.5, strawberry 1.4-2.0. Raise EC to firm up fruit quality and lower it in hot weather when transpiration is high.

Why does EC rise in a recirculating tank?

Plants take up water faster than salts in hot weather, concentrating the remainder. Top up with plain water, not feed, and check EC daily.

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