TDS to PPM Calculator
Your TDS meter says 220 — is that 220 PPM? For most drinking water, yes: TDS and PPM are used interchangeably at a 1:1 ratio. This calculator makes the label swap official.
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TDS to PPM Calculator
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Your TDS meter says 220 — is that 220 PPM? For most drinking water, yes: TDS and PPM are used interchangeably at a 1:1 ratio. This calculator makes the label swap official.
How to use this calculator
- Enter your TDS reading.
- That number is your approximate PPM.
The formula
TDS meters estimate dissolved solids; for typical freshwater the displayed TDS ≈ PPM numerically.
What the units mean
TDS (total dissolved solids) — everything dissolved in the water, which handheld meters estimate from electrical conductivity.
PPM (parts per million) — one part of solute per million parts of the total mixture. The workhorse unit for trace concentrations in water, air, and food.
Worked example
TDS meter reads 340 → approximately 340 PPM total dissolved solids.
Quick reference
| TDS reading | ≈ PPM |
|---|---|
| 50 | 50 |
| 150 | 150 |
| 300 | 300 |
| 500 | 500 |
Approximate; valid for typical freshwater.
Where you will actually use this
Water reports, filter specs, and aquarium guides all say PPM while your meter says TDS.
- Drinking water checks
- Aquarium water
- RO system monitoring
- Filter replacement timing
Mistakes that give wrong answers
- Assuming 1:1 for seawater or brines (it breaks down)
- Confusing TDS with the concentration of one specific chemical
Key takeaways
- Formula: PPM ≈ TDS (1:1 for most water sources)
- Remember: Approximate; valid for typical freshwater.
- Watch out for: Assuming 1:1 for seawater or brines (it breaks down)
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
Is TDS the same as PPM?
Approximately, for typical freshwater — 1:1.
What TDS is good for drinking water?
Below 500 PPM is the common guideline; many prefer 50–150.