# mmHg to atm Converter URL: https://speedycalculator.com/calculators/conversion/mmhg-to-atm/ Last updated: 2026-10-25 > Convert millimetres of mercury (mmHg) to standard atmospheres (atm): 1 millimetre of mercury = 0.0013157897 atm, so multiply by 0.0013157897 or divide by 759.99989. Both fields are editable, so you can also type in standard atmospheres and get millimetres of mercury back. ## Inputs - Millimetres of mercury (mmHg) ## Results - Standard atmospheres ## Formula ``` 1 mmHg = 0.0013157897 atm 1 atm = 759.99989 mmHg atm = mmHg × 0.0013157897 ``` ## Explanation One standard atmosphere is 760 mmHg, the height of mercury it supports in a barometer. Medical and laboratory readings in mmHg convert this way. ### How to use the mmHg to atm Converter - Type the number of millimetres of mercury into the **Millimetres of mercury** field. Decimals such as 380 are fine. - Read the answer in **Standard atmospheres** – it updates as you type, with no button to press. - To convert the other way, type into **Standard atmospheres** and the millimetres of mercury are recalculated. - Press **Copy results** to copy both values with the page title, or **Copy link** to share this exact conversion. This page converts only mmHg ⇄ atm. Need a different unit? Use the general pressure converter, where you can choose any “from” and “to” unit. ### How it works Both units measure pressure, so they are always in the same ratio: one millimetre of mercury equals 0.0013157897 standard atmospheres. The calculator multiplies the number of millimetres of mercury you type by 0.0013157897 to give standard atmospheres, and when you type into the standard atmospheres field it divides by the same factor to give millimetres of mercury. Because the ratio never changes, doubling the millimetres of mercury always doubles the standard atmospheres. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation). ### How to convert millimetres of mercury to standard atmospheres - Write down the value in millimetres of mercury, for example **760 mmHg**. - Multiply by the conversion factor 0.0013157897 (because 1 millimetre of mercury = 0.0013157897 atm). - 760 × 0.0013157897 = **1.0000001 atm**. - To go back from standard atmospheres to millimetres of mercury, divide by 0.0013157897 – or multiply by 759.99989. ### mmHg to atm conversion table Millimetres of mercuryStandard atmospheresStandard atmospheresMillimetres of mercury1 mmHg0.0013157897 atm1 atm759.99989 mmHg10 mmHg0.013157897 atm2 atm1,519.9998 mmHg80 mmHg0.10526317 atm5 atm3,799.9995 mmHg120 mmHg0.15789476 atm10 atm7,599.9989 mmHg380 mmHg0.50000007 atm20 atm15,199.998 mmHg700 mmHg0.92105276 atm50 atm37,999.995 mmHg760 mmHg1.0000001 atm100 atm75,999.989 mmHg800 mmHg1.0526317 atm1,000 atm759,999.89 mmHg1,000 mmHg1.3157897 atm ### What is a millimetre of mercury? Millimetres of mercury measure pressure by the height of a mercury column. Blood pressure is reported in mmHg, and 760 mmHg is one standard atmosphere. ### What is a standard atmosphere? The standard atmosphere is exactly 101,325 Pa, the average air pressure at sea level. Chemistry problems and diving depth calculations often use atm. ### Quick mental conversion For a fast estimate, multiply millimetres of mercury by about **0.0013** to get standard atmospheres; the error is about 1.2%. Use the calculator above when you need the exact figure. ### Common mistakes to avoid Mixing gauge pressure (psig, barg) with absolute pressure (psia, bara), treating bar and atm as identical, and confusing kgf/cm² with bar. ## Worked example Inputs — Millimetres of mercury: 760 mmHg. Results — **Standard atmospheres = 1.00000014 atm**. ## FAQ **How many atm is 760 mmHg?** 1 atm. **How many mmHg in 1 atm?** 760. **How do I convert millimetres of mercury to standard atmospheres?** Multiply the number of millimetres of mercury by 0.0013157897. For example, 760 mmHg × 0.0013157897 = 1.0000001 atm. **How do I convert standard atmospheres back to millimetres of mercury?** Divide by 0.0013157897 (or multiply by 759.99989), or simply type the value into the standard atmospheres field above. **What is 10 mmHg in standard atmospheres?** 10 mmHg = 0.013157897 atm. **What is 1,000 mmHg in standard atmospheres?** 1,000 mmHg = 1.3157897 atm. **Is this conversion exact?** Yes. The factor comes from the official definitions of both units (NIST and the SI), so the only difference you may see is rounding in the last displayed digit. **Can I convert to other units on this page?** This page converts only between millimetres of mercury and standard atmospheres. To pick any pressure unit, use the general pressure converter linked under Related calculators. **What formula does the mmHg to atm Converter use?** 1 mmHg = 0.0013157897 atm. ## Sources - [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811) - [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)