Fertigation EC & to PPM and Back
Converts dS/m
Convert EC (dS/m) to ppm with the nutrient factor (≈700), or go from ppm back to EC, and see the strength band. Read your meter the way your recipe is written.
Convert EC ↔ ppm
Next: EC sits at 1.5 dS/m — in the healthy feed range for most crops. Hold this strength.
ppm depends on the meter scale: 500 (NaCl), 640, or 700 (KCl). Always confirm which factor your meter uses before comparing readings.
EC and ppm — key facts
- EC to ppm
- ppm = EC × factor
- ppm to EC
- EC = ppm ÷ factor
- Nutrient factor
- ≈ 700 (0.7 scale)
- Other scales
- 500, 640
- EC measures
- total dissolved salts
- Reference temp
- corrected to 25 °C
- Manage by
- EC; ppm is a label
- Privacy
- Runs in your browser; nothing uploaded
Talk EC and ppm without losing the plot
Nutrient strength gets quoted two ways: EC, which a meter reads directly, and ppm, which recipes and labels often use. They are linked by a single factor — about 700 on the nutrient scale — so ppm = EC × factor and EC = ppm ÷ factor. The trap is the scale: a meter already chose one when it printed 'ppm', so match the factor here to your meter or you'll be out by up to 40%. EC is the honest number; ppm is a convenient label.
This tool gives the converted value, the EC, the ppm and a nutrient-strength band from whichever you enter. Use it to read your meter in EC and follow a recipe written in ppm, set a controller's target, and sanity-check the strength for the crop and stage. Pair it with the Fertigation Injection Time, Sulphur Nutrient and Spreader Uniformity tools for a full fertigation plan.
Convert both ways
EC to ppm or ppm back to EC in one place.
Match your scale
Pick the factor your meter uses (500, 640 or 700).
Check the strength
See the band so the solution suits the crop stage.
Set the controller
Turn a ppm recipe into the EC target a controller reads.
Frequently Asked Questions
How is EC converted to ppm?+
By a simple factor: ppm = EC in dS/m × the conversion factor, and EC = ppm ÷ the factor to go back. For nutrient solutions the factor is commonly about 700 (the so-called 700 or 0.7 scale). The tool does the conversion both ways and shows which way you converted plus a nutrient-strength band.
Why is the factor about 700?+
EC measures how well dissolved salts carry a current, which is only a proxy for total dissolved solids. Different ion mixes give different ppm per unit of EC, so the industry settled on empirical factors — roughly 700 (the 0.7 or '500/700' family) for typical nutrient solutions. It is an approximation, not a law of physics, which is why scales differ.
Which conversion scale should I use?+
There are three common scales: 500 (NaCl / Hanna), 640 (Eutech) and 700 (nutrient / Truncheon). Nutrient growers usually use 700. The catch is that a meter reading 'ppm' has already picked a scale, so match the factor here to your meter's scale — otherwise you will be off by up to 40%.
What is a typical nutrient-solution strength?+
It depends on crop and stage, but many vegetable and fruit solutions run roughly EC 1.5–2.5 dS/m (about 1,000–1,750 ppm on the 700 scale), with seedlings lower and mature fruiting crops higher. The tool flags a general band, but always follow your crop's recipe — strength that suits a tomato can scorch a seedling.
Should I dose by EC or by ppm?+
EC is the more honest measurement because it reads directly and doesn't depend on a chosen scale, so many growers manage solutions by EC. ppm is handy when a recipe or fertiliser label is written that way. This tool lets you read the meter in EC and talk to the recipe in ppm without mixing up the scale.
Does EC tell me which nutrients are present?+
No — EC is a total measure of dissolved salts and cannot distinguish nitrate from potassium from a build-up of unwanted sodium. Two solutions with the same EC can feed very differently. Use EC and ppm to manage overall strength, and a lab analysis or recipe to manage the balance of individual nutrients.
Does temperature affect the reading?+
Yes — conductivity rises with temperature, so EC meters usually report a value corrected to 25 °C. If your meter lacks automatic temperature compensation, readings drift with the solution's temperature. Measure near 25 °C or use a compensating meter so the EC you convert is the standardised value.
Can I convert ppm back to EC?+
Yes. Enter a ppm value and the tool divides by the conversion factor to give EC in dS/m, the reverse of the EC-to-ppm direction. This is useful when a recipe is written in ppm but your meter and controller work in EC, so you can set the target the controller understands.
Are the figures precise?+
The arithmetic is exact, but the EC-to-ppm link is inherently approximate because it depends on the ion mix and the chosen scale. Treat ppm as a convenient label and manage critical decisions by EC. Calibrate your meter regularly, match the scale, and confirm the strength suits the crop and stage.