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Use our water TDS calculator to find an estimated TDS level from EC or a dry sample. See the TDS formula, steps, and examples.
| Method | Formula |
|---|---|
| EC to TDS (estimate) | TDS (mg/L) = EC (uS/cm) x k |
| Direct Gravimetric | TDS (mg/L) = ((W2 - W1) x 1000) / V |
| Unit conversion | 1 mS/cm = 1000 uS/cm |
A water TDS calculator helps you check what is in your water. TDS means total dissolved solids. These may be salts, minerals, and other matter in water. The result often shows as mg/L or ppm.
Our tool has two ways to find TDS. Use EC for a quick estimate. Or use the dry matter left from a water sample. Think of EC as a clue, not a full list of what is in your water.
TDS (mg/L) = EC (µS/cm) × factor
EC tells how well water can carry an electric charge. The factor depends on the mix of ions in the water. A factor of 0.64 is a common start, but it may not fit each sample.
For EC of 650 µS/cm and a factor of 0.64:
TDS = 650 × 0.64 = 416 mg/L
This is an estimate, not a lab test.
TDS (mg/L) = [(dish and dry matter weight − empty dish weight) × 1000] ÷ sample size
Use mg for both weights and mL for the sample size. This method weighs the dry matter left after the water dries. A lab must use the right test steps to get a sound result.
Pick EC to TDS or the dry sample method.
For EC, enter the EC value and pick its unit.
Pick a factor, or enter your own if you know it.
For a dry sample, enter both dish weights and the sample size.
Pick the result unit, then click calculate. Read the result and steps shown on the page.
Use the right unit for each value. If EC is in mS/cm, the tool first turns it into µS/cm. This helps cut unit errors.
Say your water has an EC of 650 µS/cm. You pick a factor of 0.64.
TDS = 650 × 0.64 = 416 mg/L
For low-salt water, 416 mg/L is often close in number to 416 ppm. Yet mg/L and ppm may differ in some mixes.
For a dry sample, the empty dish weighs 50,000 mg. The dish with dry matter weighs 50,042 mg. The sample size is 500 mL.
TDS = [(50,042 − 50,000) × 1000] ÷ 500 = 84 mg/L
No one TDS value can prove that water is safe to drink. TDS can change the taste, but it does not show which things are in the water. A low TDS result does not rule out germs or harmful chemicals. A high result does not show which solids caused it.
In the US, the EPA lists 500 mg/L as a secondary water standard for TDS. This is a guide for taste, look, and other traits. It does not prove that water is safe or unsafe on its own. If you worry about tap or well water, use a certified lab and check local advice.
A water TDS calculator gives you a fast way to check dissolved solids. Use EC for a quick estimate. Use dry sample weights when you have them. The factor can change the result, so treat EC-based TDS as an estimate. TDS is one clue, not the whole story.
For an EC estimate, multiply EC in µS/cm by a fit factor. For a dry sample, take the empty dish weight from the dish plus dry matter. Then multiply by 1000 and divide by the sample size in mL.
No. TDS counts dissolved matter as a whole. It does not name each item or prove that water is safe.
They are often close for dilute water. The exact link can vary by mix.
No. A TDS meter uses EC to estimate dissolved solids. It cannot find all germs, metals, or chemicals. Use the right lab test for each concern.