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mmHg to Kilopascals Converter
↔ Convert kPa to mmHg instead

Common Conversions

mmHg kPa
1 0.1333
10 1.333
23.8 3.173
50 6.666
100 13.332
120 15.999
200 26.664
400 53.329
500 66.661
760 101.325
1000 133.322
1520 202.65

Why this conversion matters in chemistry

Clinical literature reports pressures in mmHg almost universally — 120/80 blood pressure, arterial oxygen partial pressures, vapor pressures from older chemistry references. Modern SI-aligned journals and physiology papers from the UK and EU tend to quote the same quantities in kPa. Multiplying mmHg by 0.13332 does the conversion. 760 mmHg becomes 101.325 kPa; 23.8 mmHg (water vapor pressure at 25°C) becomes 3.17 kPa. The factor is exact, derived from the defining equivalence 1 atm = 760 mmHg = 101.325 kPa. Reading across conventions is usually easier than recalculating.

Formula

kPa = mmHg × 0.13332

Worked Examples

760 mmHg = 101.325 kPa

Sea-level atmospheric pressure — the anchor that ties mmHg and kPa together via the 1 atm equivalence.

120 mmHg = 16.0 kPa

A typical systolic blood pressure reading. The 120/80 mmHg convention is deeply entrenched in medical reporting.

23.8 mmHg = 3.17 kPa

Water's vapor pressure at 25°C. The correction subtracted from measured total pressure when collecting a gas over water.

400 mmHg = 53.3 kPa

Roughly half an atmosphere — a useful vacuum setting for distilling moderately volatile organic solvents on a rotovap.

Frequently Asked Questions

How do I convert mmHg to kPa?
Multiply by 0.13332. So 760 mmHg becomes 101.325 kPa, and 400 mmHg becomes 53.3 kPa. The factor is derived from the exact equivalence 1 atm = 760 mmHg = 101.325 kPa.
Why is mmHg still around in chemistry?
Mostly historical inertia plus practical readability. The unit dates back to Torricelli's 1643 mercury barometer, and vapor-pressure tables, manometer readings, and clinical data have all stayed in mmHg while the rest of science migrated to SI. For vacuum chemistry the numbers also happen to read cleanly in mmHg, which has kept it useful.
Are mmHg and torr the same?
For every practical purpose, yes. The strict definitions differ by less than 2 parts in 10⁷ — far below any precision you'd care about at the bench. The torr is pinned to exactly 1/760 atm; mmHg technically depends on mercury density at a defined temperature and gravity. Treat them as interchangeable.
How does mmHg feed into vapor-pressure calculations?
A lot of classic vapor-pressure data is tabulated in mmHg. Before dropping those values into Clausius–Clapeyron or Raoult's-law calculations with SI-based thermodynamic constants, convert to kPa or Pa. Water's vapor pressure at 25°C is 23.8 mmHg, or 3.17 kPa — the number that typically subtracts from a measured reading when collecting a gas over water, to recover the dry-gas partial pressure.