EC-TDS Salinity & dS/m to ppm, and the Class
Reads water
Convert electrical conductivity (EC, dS/m) to total dissolved solids (TDS, ppm)and back with TDS ≈ EC × 640, and read the salinity class — so you know whether sensitive crops will suffer.
EC ↔ TDS converter
Next: treat water as slight salinity hazard (EC 2 dS/m); for sensitive crops above the slight band, leach with extra water or blend with a low-EC source.
The EC→TDS factor varies with ion mix (typically 640–700 for irrigation/groundwater); use your meter's stated factor for best accuracy.
EC-TDS salinity — key facts
- EC units
- dS/m (deciSiemens/m)
- TDS units
- ppm (mg/L)
- Conversion
- TDS ≈ EC × 640
- 1 dS/m
- ≈ 640 ppm
- Factor range
- ~550–700
- Safe water
- < 0.7 dS/m
- Severe
- > 3.0 dS/m
- Privacy
- Runs in your browser; nothing uploaded
One number, two units — and what it means for your crop
Salinity is the silent yield-killer: dissolved salts raise the osmotic pull on soil water so roots strain to drink even when the soil looks moist. That salinity is reported two ways — as electrical conductivity (EC) in dS/m or as total dissolved solids (TDS) in ppm — and the two convert with the agricultural rule of thumb TDS ≈ EC × 640. Knowing one lets you read the other, and the salinity class tells you whether sensitive crops are at risk.
This converter returns the converted value, the conversion factor used, the EC value and the salinity class from whichever figure you have. Use it to read meter outputs, compare water sources, and judge crop suitability at a glance. Pair it with the Soil Salinity (EC), Irrigation Water SAR and RSC & Gypsum tools for a full water-quality assessment.
Convert either way
EC to TDS or TDS to EC in a tap.
Read the salinity class
See if water sits safe, moderate or severe.
Protect sensitive crops
Spot trouble before yield drops.
Compare water sources
Judge bores and supplies on one scale.
Frequently Asked Questions
What are EC and TDS?+
Electrical conductivity (EC) measures how well water or a soil solution conducts electricity, which rises with dissolved salts; it is reported in deciSiemens per metre (dS/m). Total dissolved solids (TDS) measures the mass of those salts, reported in parts per million (ppm) or mg/L. Both describe salinity from different angles.
How do EC and TDS convert?+
They are linked by an empirical factor — for agricultural water and soil the common rule is TDS (ppm) ≈ EC (dS/m) × 640. So an EC of 1 dS/m corresponds to roughly 640 ppm of dissolved salts. This converter applies that factor in both directions and reports the factor it used.
Why does the conversion factor vary?+
The factor depends on which salts dominate the water. Around 640 suits most mixed irrigation and groundwater, but values from about 550 to 700 are used; high-sulphate or high-bicarbonate waters sit at the lower end and chloride-rich waters at the higher. Use 640 unless a local standard or lab specifies otherwise.
Why does salinity matter for crops?+
Dissolved salts raise the osmotic pressure of soil water, making it harder for roots to take up moisture — so a salty solution can leave plants drought-stressed even in wet soil. High salinity stunts growth, scorches leaf margins and cuts yield, and sensitive crops suffer well before tolerant ones.
What is the salinity class?+
It is a band that tells you how salty the water or soil is and which crops will cope. As a guide for irrigation water, under about 0.7 dS/m is generally safe, 0.7–3.0 dS/m carries slight to moderate restriction, and above 3.0 dS/m brings severe limits suited only to salt-tolerant crops. The converter flags the class for your value.
Which crops are sensitive to salinity?+
Beans, carrots, onions, strawberries and many fruit trees are salt-sensitive and decline at low EC. Cereals like wheat and tolerant crops such as barley, cotton, date palm and many grasses handle far higher salinity. Always check the threshold for your specific crop against the EC class.
How do I measure EC or TDS?+
An EC or conductivity meter reads dS/m directly; many handheld meters labelled TDS actually measure EC and apply a built-in factor to display ppm. For soil, EC is measured on a saturated paste or a soil-to-water extract. Always note the temperature, since EC rises with warmth and meters usually correct to 25°C.
Is soil EC the same as water EC?+
They use the same units but are measured differently — soil EC depends on the extract ratio (saturated paste, 1:1, 1:5). A saturated-paste EC is the standard for crop tolerance thresholds, while diluted extracts read lower and need their own interpretation. Match your reading to the method the thresholds assume.
Can I reduce salinity?+
Yes — leaching with good-quality water flushes salts below the root zone, choosing tolerant crops sidesteps the problem, and improving drainage stops salts re-accumulating. For sodium-affected water, gypsum and management help. Knowing the EC and class is the first step in deciding which of these you need.
Are the figures precise?+
The conversion is exact for the factor chosen, but the right factor and the salinity thresholds depend on salt composition, crop, soil and measurement method. Treat the converted value and class as a sound guide, and confirm against a laboratory analysis and your crop's specific tolerance.