ConverterHub

Salinity (%) to Practical salinity units Converter

Enter a value in salinity (%) to convert it to practical salinity units, parts per thousand.

Result

35.00 PSU
35.00 ppt

How it is calculated

The tool treats the salinity you enter as a mass percentage of salt in the water (grams of salt per 100 g) and multiplies by ten: ppt = S% × 10 and PSU = S% × 10. A percentage is parts per hundred and a per-mille is parts per thousand, ten times finer, so 1% equals 10 parts per thousand. The tool shows the same number for both outputs, to two decimals, because it takes 1 PSU as numerically equal to 1 ppt. That is a close approximation for seawater, not the real PSU, which comes from a conductivity measurement. Values from 0 to 34 (%) are accepted, since about 34% is the saltiest natural water; a negative number or anything above 34 gives no result, so a ppt figure such as 35 typed into the percentage box is rejected.

Worked example

A reading of 3.5% salinity is typical of open seawater. Multiply by ten: 3.5 × 10 = 35. The tool shows 35.00 PSU and also 35.00 ppt. In other words, each kilogram of that water contains roughly 35 grams of dissolved salt. A brackish sample at 0.5% would give 5.00 PSU in the same way.

Try this example →

Common mistakes

  • Entering a value that is already in ppt or PSU (35) in the percentage field. Anything above 34 is rejected, so no result appears; type 3.5 for seawater instead.
  • Entering the percentage as a fraction (0.035) instead of 3.5; the answer would be 0.35 PSU, one hundred times too small.
  • Treating the PSU result as a conductivity-derived measurement: here it is only the percentage multiplied by ten, so it is not a replacement for a calibrated instrument reading.
  • Using the result for very precise oceanographic work, where PSU and absolute salinity (g/kg) differ slightly.
  • Expecting the PSU and ppt lines to differ; the tool gives the same number for both.

About this calculator

Modern oceanography measures seawater salt content as Practical Salinity Units (PSU), derived from the Practical Salinity Scale (PSS-78) by comparing a sample's electrical conductivity to a standard KCl solution — a method precise and repeatable enough to have replaced older chemical (chlorinity-based) salinity determinations. PSU is dimensionless but numerically tracks almost 1:1 with the older “parts per thousand (‰)” convention, since both center on average open-ocean salinity of about 35.

This converter does not work from conductivity: you enter salinity as a percentage and it multiplies by 10 to give the equivalent in parts per thousand, which it reports as PSU (3.5% → 35). Oceanographers and marine biologists rely on PSU readings from CTD (conductivity-temperature-depth) instruments to study water-mass mixing, density-driven currents, and habitat suitability for marine species, and a percentage-to-PSU conversion is handy when reconciling older records with modern data.

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