| Input | From | To | Result |
|---|---|---|---|
| 1200 | µS/cm | ppm (500 scale) | 600.00 |
| 1.8 | mS/cm | ppm (640 scale) | 1152.00 |
| 2.2 | dS/m | ppm (700 scale) | 1540.00 |
| 950 | ppm (500 scale) | µS/cm | 1900.00 |
- Unit baseline: Convert everything to µS/cm first.
- EC units: 1 mS/cm = 1 dS/m and 1 mS/cm = 1000 µS/cm.
- ppm estimate: ppm = µS/cm × factor, where factor is 0.50, 0.64, or 0.70.
- Temperature compensation (optional): ECref = ECmeasured ÷ (1 + α × (T − Tref)).
- Measure your solution with your meter and note the unit.
- Enter the reading and choose the matching From unit.
- Select your desired output in the To unit.
- Enable temperature compensation if your solution is far from 25°C.
- Press Convert to see the result above the form.
- Download CSV or PDF to save and share the conversion.
Why EC is the preferred control signal
Electrical conductivity (EC) reflects total ionic strength in nutrient solution, so it changes immediately after fertilizer additions, dilution, or evaporation. It cannot describe which ions are present, yet it remains the fastest operational check for “feed strength”. For dependable comparisons, measure at similar temperatures and report the unit used.
How ppm scales map from conductivity
Most “ppm” readings are calculated from EC rather than measured as dissolved mass. Meters apply a factor to convert µS/cm into a ppm estimate. Common factors are 0.50 (500), 0.64 (640), and 0.70 (700). Two gardeners can see different ppm for the same solution if their meters use different factors. This calculator converts across these scales for clearer communication.
Temperature impact and compensation logic
Conductivity rises as temperature increases, often near 2% per °C for typical nutrient mixes. When solution temperature is far from the 25°C reference, compensation helps avoid overfeeding in warm tanks and underfeeding in cool reservoirs. The calculator applies ECref = ECmeasured ÷ (1 + α × (T − Tref)). Use the meter’s coefficient if it differs from the default.
Turning conversions into mixing decisions
Convert your measurement into the unit your recipe chart uses, then compare against the target range for your crop stage. If EC is high, add plain water, circulate, and recheck. If EC is low, add nutrients gradually, mix thoroughly, and measure again. Record input value, scale, temperature, and target to keep adjustments consistent across days. Exporting your results as CSV or PDF supports batch comparisons, audit trails, and team handoffs, especially when multiple growers follow one nutrient program across sites weekly.
Checks that improve repeatability
Rinse and clean probes, calibrate with fresh standard solution, and avoid air bubbles around electrodes. Sample from the same location after circulation stabilizes. Prevent carryover by rinsing between mixes. When sharing numbers, always state µS/cm, mS/cm, dS/m, or the ppm factor used, and whether readings were temperature-compensated. Consistent reporting makes shared nutrient schedules more reliable.
1) Is ppm the same as true total dissolved solids?
No. Meter ppm is a calculated estimate from conductivity. True TDS requires laboratory-style measurement of dissolved mass, and results vary with the ions present.
2) Which ppm scale should I use for my garden?
Use the scale your meter displays by default (500, 640, or 700). Staying consistent avoids confusion when comparing recipes, logs, and feeding charts.
3) Why do my EC readings change with temperature?
Warmer solutions conduct electricity better, so EC rises. Cooler solutions conduct less, so EC falls. Compensation normalizes the reading to a reference temperature.
4) Does 1 mS/cm always equal 1 dS/m?
Yes. In horticulture and irrigation, 1 mS/cm is numerically equal to 1 dS/m. The names differ, but the magnitude is the same.
5) Can I compare EC between different nutrient brands?
You can compare overall strength, but not exact composition. Different formulas may reach the same EC with different ion ratios, so follow label guidelines for balanced nutrition.
6) What if my meter auto-compensates temperature already?
If your meter reports a compensated EC (often “ATC”), you can leave compensation off here. Use compensation only when you are converting an uncompensated measured value.