Torr to kPa Converter
Common Conversions
| torr | kPa |
|---|---|
| 1 | 0.133 |
| 5 | 0.667 |
| 10 | 1.333 |
| 25 | 3.333 |
| 50 | 6.666 |
| 100 | 13.332 |
| 200 | 26.664 |
| 400 | 53.329 |
| 500 | 66.661 |
| 600 | 79.993 |
| 760 | 101.325 |
| 1000 | 133.322 |
Why this conversion matters in chemistry
Vacuum gauges read in torr, safety documentation is written in kPa, and both describe the same physical pressure. The factor is 0.133322 kPa per torr — a number that drops straight out of the definition, since 760 torr equals one standard atmosphere equals 101.325 kPa. Reach for the conversion when a sublimation recipe reports a target of 100 torr and an SI-aligned process sheet wants that value as 13.3 kPa, or when a vapor-pressure table ends in torr and a Clausius-Clapeyron fit has the rest of its data in kPa.
Formula
Where the factor comes from
The pascal is assembled rather than declared: a newton per square meter, falling straight out of the SI base units with nothing chosen for tidiness. The torr is its opposite, a fixed fraction — exactly 1/760 of the standard atmosphere. Since that atmosphere is itself defined as exactly 101325 Pa, which is exactly 101.325 kPa, the factor turns out to be a quotient of two numbers already printed on gauges: 101.325 divided by 760 gives 0.13332236842105… kPa per torr. The kilo prefix contributes exactly 10³ and no uncertainty of its own. Nothing was measured anywhere in that chain, so the relation is exact; the decimal recurs only because 760 is not a power of ten, and 101.325/760 remains the shortest honest way to write it.
Precision and significant figures
Five figures — 0.13332 — sit within two parts in a hundred thousand of exact, and three are enough for most bench purposes. The pair is unusually well matched in magnitude, which helps: a three-figure torr reading converts to a three-figure kPa value, so nothing needs padding or trimming on the way across. Rounding the factor to 0.13 is the one shortcut worth refusing. It runs 2.5 percent low every time and never averages out, so a 600 torr barometric reading comes out as 78.0 kPa against a true 79.99 — a two-kilopascal bias parked in the middle of a Clausius-Clapeyron fit or a mole count.
Worked Examples
Standard atmospheric pressure, expressed in the SI-derived unit of choice for modern documentation.
The factor itself. A useful number to keep in mind when scanning a vacuum gauge.
The vapor pressure of water at 25 °C — worth tracking any time a gas is being collected over water.
A moderate rotary-evaporator vacuum, enough to bring most common solvents off at a reasonable bath temperature.
Common mistakes
Vacuum gauges read absolute, kPa specs often gauge
A torr reading from a vacuum gauge is absolute by construction. Process and equipment documentation frequently writes kPag or kPa(g), referenced to the room. Setting a converted 13.3 kPa absolute against a limit written as gauge pressure leaves the two roughly 101 kPa apart, and neither number carries anything to signal the mismatch. Confirm the reference before comparing.
A fitted intercept does not survive unit change
Plot ln p against 1/T and the slope, −ΔHvap/R, is indifferent to whether p is in torr or kilopascals. The intercept is not: re-expressing a torr dataset in kPa shifts it by ln(0.133322), about −2.015. Reusing a published intercept alongside converted pressures produces vapor pressures wrong by a factor of roughly 7.5 while the enthalpy still looks correct.
Round converted limits inward, not to tidy numbers
A hold-below figure of 13 kPa is 97.5 torr. Writing it as 100 torr because the number looks better relaxes the constraint by two and a half percent, and rounding the other way tightens it. Converted specification values should be rounded in the conservative direction rather than to the nearest round figure, and the original unit kept beside them.