Convert Torr to Millimetre of mercury
1 torr = 0.9999999 millimetre of mercury (mmHg). For example, 10 torr = 9.999999 millimetre of mercury and 100 torr = 99.99999 millimetre of mercury. Type any value below to convert torr to millimetre of mercury both ways — it runs entirely in your browser.
Quick answer: Torr to Millimetre of mercury
1 Torr = 0.9999999 Millimetre of mercury (Torr → mmHg). To convert torr to millimetre of mercury, multiply by 0.9999999. To convert millimetre of mercury to torr, multiply by 1. The converter at the top does this instantly and both ways; the sections below give the formula, worked examples, a full conversion chart and answers to the most common torr-to-millimetre of mercury questions.
How to convert Torr to Millimetre of mercury
To convert torr to millimetre of mercury, multiply the number of torr by the conversion factor 0.9999999, because 1 Torr = 0.9999999 mmHg. The conversion is linear, so the same factor works for any value — whole numbers, decimals or fractions. For the reverse direction, 1 mmHg = 1 Torr, so you divide by 0.9999999 (or multiply by 1) to turn millimetre of mercury back into torr.
mmHg = Torr × 0.9999999 ·
Torr = mmHg × 1
- Write down the value you want to convert, in torr.
- Multiply it by 0.9999999.
- The result is the same area/length/quantity expressed in millimetre of mercury.
Torr to Millimetre of mercury — worked examples
Each row shows the exact arithmetic so you can follow the conversion step by step. For example, 5 torr is 4.999999 millimetre of mercury because 5 Torr × 0.9999999 = 4.999999 mmHg.
| Torr | Calculation | Millimetre of mercury |
|---|---|---|
| 1 Torr | 1 Torr × 0.9999999 = 0.9999999 mmHg | 0.9999999 mmHg |
| 2 Torr | 2 Torr × 0.9999999 = 2 mmHg | 2 mmHg |
| 3 Torr | 3 Torr × 0.9999999 = 3 mmHg | 3 mmHg |
| 5 Torr | 5 Torr × 0.9999999 = 4.999999 mmHg | 4.999999 mmHg |
| 7 Torr | 7 Torr × 0.9999999 = 6.999999 mmHg | 6.999999 mmHg |
| 10 Torr | 10 Torr × 0.9999999 = 9.999999 mmHg | 9.999999 mmHg |
| 12 Torr | 12 Torr × 0.9999999 = 12 mmHg | 12 mmHg |
| 15 Torr | 15 Torr × 0.9999999 = 15 mmHg | 15 mmHg |
| 20 Torr | 20 Torr × 0.9999999 = 20 mmHg | 20 mmHg |
| 25 Torr | 25 Torr × 0.9999999 = 25 mmHg | 25 mmHg |
| 50 Torr | 50 Torr × 0.9999999 = 49.99999 mmHg | 49.99999 mmHg |
| 100 Torr | 100 Torr × 0.9999999 = 99.99999 mmHg | 99.99999 mmHg |
Common Torr to Millimetre of mercury conversions
These are the torr-to-millimetre of mercury values people look up most often. Every figure is computed from the exact factor, so you can rely on them for quick reference:
- 1 torr = 0.9999999 millimetre of mercury
- 2 torr = 2 millimetre of mercury
- 2.5 torr = 2.5 millimetre of mercury
- 3 torr = 3 millimetre of mercury
- 4 torr = 3.999999 millimetre of mercury
- 5 torr = 4.999999 millimetre of mercury
- 6 torr = 5.999999 millimetre of mercury
- 7 torr = 6.999999 millimetre of mercury
- 8 torr = 7.999999 millimetre of mercury
- 9 torr = 8.999999 millimetre of mercury
- 10 torr = 9.999999 millimetre of mercury
- 12 torr = 12 millimetre of mercury
- 15 torr = 15 millimetre of mercury
- 20 torr = 20 millimetre of mercury
- 25 torr = 25 millimetre of mercury
- 30 torr = 30 millimetre of mercury
- 50 torr = 49.99999 millimetre of mercury
- 75 torr = 74.99999 millimetre of mercury
- 100 torr = 99.99999 millimetre of mercury
- 200 torr = 200 millimetre of mercury
- 500 torr = 499.9999 millimetre of mercury
- 1000 torr = 999.9999 millimetre of mercury
Torr to Millimetre of mercury conversion chart (both directions)
The chart below converts torr to millimetre of mercury and millimetre of mercury to torr side by side, so it works whichever way you need. 1 torr = 0.9999999 millimetre of mercury, and 1 millimetre of mercury = 1 torr.
| Torr → Millimetre of mercury | Millimetre of mercury → Torr |
|---|---|
| 0.25 Torr = 0.25 mmHg | 0.25 mmHg = 0.25 Torr |
| 0.5 Torr = 0.4999999 mmHg | 0.5 mmHg = 0.5000001 Torr |
| 1 Torr = 0.9999999 mmHg | 1 mmHg = 1 Torr |
| 2 Torr = 2 mmHg | 2 mmHg = 2 Torr |
| 3 Torr = 3 mmHg | 3 mmHg = 3 Torr |
| 4 Torr = 3.999999 mmHg | 4 mmHg = 4.000001 Torr |
| 5 Torr = 4.999999 mmHg | 5 mmHg = 5.000001 Torr |
| 6 Torr = 5.999999 mmHg | 6 mmHg = 6.000001 Torr |
| 7 Torr = 6.999999 mmHg | 7 mmHg = 7.000001 Torr |
| 8 Torr = 7.999999 mmHg | 8 mmHg = 8.000001 Torr |
| 9 Torr = 8.999999 mmHg | 9 mmHg = 9.000001 Torr |
| 10 Torr = 9.999999 mmHg | 10 mmHg = 10 Torr |
| 12 Torr = 12 mmHg | 12 mmHg = 12 Torr |
| 15 Torr = 15 mmHg | 15 mmHg = 15 Torr |
| 20 Torr = 20 mmHg | 20 mmHg = 20 Torr |
| 25 Torr = 25 mmHg | 25 mmHg = 25 Torr |
| 30 Torr = 30 mmHg | 30 mmHg = 30 Torr |
| 40 Torr = 39.99999 mmHg | 40 mmHg = 40.00001 Torr |
| 50 Torr = 49.99999 mmHg | 50 mmHg = 50.00001 Torr |
| 75 Torr = 74.99999 mmHg | 75 mmHg = 75.00001 Torr |
| 100 Torr = 99.99999 mmHg | 100 mmHg = 100 Torr |
| 150 Torr = 150 mmHg | 150 mmHg = 150 Torr |
| 200 Torr = 200 mmHg | 200 mmHg = 200 Torr |
| 250 Torr = 250 mmHg | 250 mmHg = 250 Torr |
| 500 Torr = 499.9999 mmHg | 500 mmHg = 500.0001 Torr |
| 1000 Torr = 999.9999 mmHg | 1000 mmHg = 1,000 Torr |
Torr vs Millimetre of mercury: which is bigger?
A millimetre of mercury is the larger unit: one millimetre of mercury equals 1 torrs. Put another way, you need 1 torrs to make a single millimetre of mercury.
What is a Torr? History, origin and usage
The torr honours Evangelista Torricelli, who built the first mercury barometer in 1643 and correctly explained that the column was held up by the weight of the air outside. The unit was named in the 1940s, and was defined as exactly one 760th of a standard atmosphere so that it would be tied to a fixed number rather than to the behaviour of real mercury.
Torr is the working unit of vacuum technology — vacuum pumps, freeze dryers, electron microscopes, semiconductor process chambers and mass spectrometers are all specified in torr or its subdivisions.
Because it is defined as a 760th of an atmosphere, 760 torr is one atmosphere exactly, by construction. It is very nearly the same as a millimetre of mercury but not exactly: the two differ by about one part in seven million, a gap that matters only in precision metrology and is the reason careful documents never treat the two names as interchangeable.
What is a Millimetre of mercury? History, origin and usage
Measuring pressure by the height of a mercury column dates to Torricelli in 1643 and became the standard laboratory method for three centuries. Mercury was chosen because it is dense enough to keep the tube a manageable length — a water barometer measuring the same pressure would need to be over ten metres tall. The modern unit no longer depends on real mercury: it is fixed at exactly 133.322387415 pascals, the value a millimetre of mercury would give at a conventional density of 13,595.1 kg per cubic metre under standard gravity.
Millimetres of mercury are the universal unit of blood pressure — a reading of "120 over 80" means 120 mmHg when the heart contracts and 80 mmHg between beats. They are also used for eye pressure, cerebrospinal fluid pressure and some vacuum work.
Mercury sphygmomanometers are being retired worldwide because of the toxicity of mercury, yet the unit has outlived the instrument: digital monitors with no mercury in them still report in mmHg, because a century of medical guidance is written in it.
Convert 1 Torr to other units
It can help to see a torr next to the other units it is commonly compared with. One torr (Torr) is equal to:
| 1 Torr equals | Unit |
|---|---|
| 133.3224 Pa | Pascal |
| 1.333224 hPa | Hectopascal |
| 0.1333224 kPa | Kilopascal |
| 0.0001333224 MPa | Megapascal |
| 1.333224 mbar | Millibar |
| 0.001333224 bar | Bar |
| 0.001315789 atm | Standard atmosphere |
| 0.9999999 mmHg | Millimetre of mercury |
| 0.03937007 inHg | Inch of mercury |
| 13.5951 mmH₂O | Millimetre of water |
| 0.5352401 inH₂O | Inch of water |
| 0.01933677 psi | Pound per square inch |
| 0.00135951 kgf/cm² | Kilogram-force per square centimetre |
Convert 1 Millimetre of mercury to other units
One millimetre of mercury (mmHg) is equal to:
| 1 Millimetre of mercury equals | Unit |
|---|---|
| 133.3224 Pa | Pascal |
| 1.333224 hPa | Hectopascal |
| 0.1333224 kPa | Kilopascal |
| 0.0001333224 MPa | Megapascal |
| 1.333224 mbar | Millibar |
| 0.001333224 bar | Bar |
| 0.00131579 atm | Standard atmosphere |
| 1 Torr | Torr |
| 0.03937008 inHg | Inch of mercury |
| 13.5951 mmH₂O | Millimetre of water |
| 0.5352402 inH₂O | Inch of water |
| 0.01933678 psi | Pound per square inch |
| 0.00135951 kgf/cm² | Kilogram-force per square centimetre |
Tips for converting Torr to Millimetre of mercury
- To go from torr to millimetre of mercury, multiply by 0.9999999; to go back, divide by 0.9999999 (or multiply by 1).
- For a quick mental estimate, remember that 1 torr ≈ 0.9999999 millimetre of mercury, so 10 torr ≈ 9.999999 millimetre of mercury.
- The converter above keeps full precision; the tables round for readability, so use the tool for exact figures.
- Both fields update live as you type — change either side to convert in that direction.
How to use this Torr to Millimetre of mercury converter
Type a number into the Torr field and the equivalent in Millimetre of mercury appears instantly — there is no “convert” button to press and nothing is sent to a server, so it works offline once the page has loaded and is safe for any data. You can also type into the Millimetre of mercury field to convert the other way (millimetre of mercury to torr). Use the swap control to flip the two units, and copy the result with a single click. Because the calculation runs in your browser with full floating-point precision, the converter is more exact than the rounded figures shown in the reference chart above — use the chart for quick look-ups and the tool for precise work.
Accuracy and method
Every figure on this page — the formula, the worked examples, the conversion chart and the “convert to other units” tables — is computed from a single verified conversion factor (1 Torr = 0.9999999 mmHg), never copied from a hand-typed lookup table that could drift. That factor is derived from each unit’s definition in terms of a common base unit, and an automated check re-verifies all of the site’s factors on every update, so the numbers here stay correct over time. This matters for torr-to-millimetre of mercury conversions because a small rounding error in a published table compounds quickly at larger quantities; computing from the exact factor avoids that.
Sources
- BIPM — The International System of Units (SI Brochure) — the defining document for the SI, published by the International Bureau of Weights and Measures. It fixes the base unit that this conversion resolves to, which is why the factor here can be exact rather than approximate.
- NIST — Definitions of the SI base units — the US National Institute of Standards and Technology reference for the SI base units, used here as an independent cross-check on the base-unit definition.
Pressure factors here come from fixed definitions, anchored to the pascal: a bar is exactly 100,000 Pa, one atmosphere is exactly 101,325 Pa, a torr is exactly a 760th of an atmosphere, and psi is built from the exact pound and the exact inch. Two of them — psi and the torr — work out to decimals that repeat forever, so where a number is shown rounded it is marked, not quietly trimmed.
Frequently asked questions
- How many millimetre of mercury are in 1 torr?
- 1 torr = 0.9999999 millimetre of mercury (mmHg). To convert any number of torr to millimetre of mercury, multiply by 0.9999999.
- How do I convert torr to millimetre of mercury?
- Multiply the number of torr by 0.9999999. For example, 10 torr = 10 × 0.9999999 = 9.999999 millimetre of mercury, and 25 torr = 25 millimetre of mercury.
- How many torr are in 1 millimetre of mercury?
- 1 millimetre of mercury = 1 torr. So to convert millimetre of mercury back to torr, multiply by 1.
- What is the formula to convert torr to millimetre of mercury?
- millimetre of mercury = torr × 0.9999999. The reverse formula is torr = millimetre of mercury × 1.
- How much is 100 torr in millimetre of mercury?
- 100 torr = 99.99999 millimetre of mercury. (And 1000 torr = 999.9999 millimetre of mercury.)
- Which is bigger, a torr or a millimetre of mercury?
- A millimetre of mercury is larger: 1 millimetre of mercury = 1 torr.
- Is this torr to millimetre of mercury converter accurate?
- Yes — every value is computed from the exact 0.9999999 mmHg per Torr factor (not rounded look-up tables), and the factors are re-verified automatically on every update.
- Can I convert millimetre of mercury to torr too?
- Yes. The converter works both ways — enter a value in either field. 1 millimetre of mercury = 1 torr.