EC ↔ ppm converter
Convert a reading between EC and the three ppm scales meters use.
Your reading
A ppm meter measures conductivity and multiplies by a fixed factor. Different brands use different factors, so the same solution reads differently. EC is the unambiguous unit; compare feeds in EC.
On every scale
EC
1.8mS/cm
500 scale (NaCl, 'TDS')
900ppm
640 scale
1,152ppm
700 scale (442, 'KCl')
1,260ppm
How your reading compares
- feed EC· flower · soilless or hydroponic1.5–2.5 mS/cmModerate— your 1.8 mS/cm is within this range
- feed EC (no-benefit ceiling)· flower · hydroponic≤ 4 mS/cmModerate— your 1.8 mS/cm is within this limit
- feed EC (yield-loss threshold)· flower · stone wool≥ 8 mS/cmModerate— your 1.8 mS/cm is below this limit
- irrigation solution EC for cuttings· propagation · peat pellets1.2 mS/cmModerate— your 1.8 mS/cm is above this range
How this is calculated
ppm = EC (mS/cm) × scale factor; EC = ppm / scale factor; 1 mS/cm = 1000 µS/cm
- Meters disagree because they use different conversion factors; EC is the unambiguous unit.
Cited targets
From the genetics.guru grow library, in the units each source used. Grades: strong and moderate are peer-reviewed; community practice is untested.
feed ECflower · soilless or hydroponic1.5–2.5 mS/cmModerate
range spanned by trials with no yield penalty; 4 mS/cm gave no extra yield or cannabinoids (Hershkowitz 2025)
3 sources
- Bevan L, Jones M, Zheng Y (2021). Optimisation of Nitrogen, Phosphorus, and Potassium for Soilless Production of Cannabis sativa in the Flowering Stage Using Response Surface Analysis
- Westmoreland FM, Bugbee B (2022). Sustainable Cannabis Nutrition: Elevated root-zone phosphorus significantly increases leachate P and does not improve yield or quality
- Hershkowitz JA, Westmoreland FM, Bugbee B (2025). Elevated root-zone P and nutrient concentration do not increase yield or cannabinoids in medical cannabis
feed EC (no-benefit ceiling)flower · hydroponic≤ 4 mS/cmModerate
no yield/quality gain from 2 -> 4 mS/cm; 1.8 vs 3 no difference (Baas & Wijnen via Hershkowitz)
2 sources
feed EC (yield-loss threshold)flower · stone wool≥ 8 mS/cmModerate
8 mS/cm cut height 15% and flower yield ~20% in some cultivar/treatment combinations; cannabinoids unchanged
1 source
irrigation solution EC for cuttingspropagation · peat pellets1.2 mS/cmModerate
Protocol value (pH ~5.8); in aeroponics higher nutrient concentrations improved rooting.
2 sources
- Campbell LG, Naraine SGU, Dusfresne J (2019-03-18). Phenotypic plasticity influences the success of clonal propagation in industrial pharmaceutical Cannabis sativa — PLOS ONE 14(3):e0213434
- Weingarten M, Mattson N, Grab H (2024-04-30). Evaluating Propagation Techniques for Cannabis sativa L. Cultivation: A Comparative Analysis of Soilless Methods and Aeroponic Parameters — Plants 13(9):1256