To convert millitorr to atmospheres, multiply by 1.315789474e-06. That factor is the whole relationship: both units measure pressure, so the conversion is a proportion with no offset and no substance-specific constant.
Standard atmospheric pressure by definition — 101,325 pascals exactly. One thousandth of a torr, the working unit of vacuum deposition.
Gauge versus absolute. A tyre gauge reading 32 psi means 32 psi above atmospheric, which is about 46.7 psi absolute. Converting the number is straightforward; remembering which zero it was measured from is where the mistakes happen. N/mm² and MPa are the same size, so a drawing quoting either is quoting the same stress. The tables underneath give both a plain step-by-step lookup and a list of real quantities expressed in atmospheres, so you can sanity-check whether your answer is a plausible size.
The formula
millitorr- The amount you are converting, in millitorr
1.31578947368e-06- The exact number of atmospheres in one millitorr
atmospheres- The converted result
How it works, step by step
- Enter the value in millitorr.
- It is multiplied by 1.31578947368e-06, the exact factor between the two units.
- The answer is shown in atmospheres, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A bicycle tyre: 4.65e+06 mTorr in atmospheres
Take a bicycle tyre, roughly 4.65e+06 mTorr. The conversion is a single multiplication — 4.65e+06 × 1.31579e-06 — giving 6.11842 atm. Because the relationship is proportional, doubling the input doubles the answer to 12.2368 atm.
Sea-level air: 7.6e+05 mTorr in atmospheres
At 7.6e+05 mTorr (sea-level air), the same quantity in atmospheres is 7.6e+05 × 1.31579e-06 = 1 atm. One millitorr is 1.31579e-06 atmospheres, so the numbers shrink as expected.
How to read your score
Frequently asked questions
How many atmospheres are in one millitorr?
Exactly 1.31578947368e-06. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert millitorr to atmospheres?
atmospheres = millitorr × 1.31578947368e-06. Reversed, millitorr = atmospheres ÷ 1.31578947368e-06, which is the same as multiplying by 760,000.
Which is the bigger unit, the millitorr or the atmosphere?
The atmosphere. One millitorr is only 1.31579e-06 of a atmosphere, so it takes 760,000 millitorr to make one atmosphere.
What does this quantity actually measure?
Both units measure pressure. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a millitorr?
One thousandth of a torr, the working unit of vacuum deposition.
What is a atmosphere?
Standard atmospheric pressure by definition — 101,325 pascals exactly.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Millitorr to atmospheres reference tables
| Millitorr | Atmospheres |
|---|---|
| 0.5 mTorr | 6.57895e-07 atm |
| 1 mTorr | 1.31579e-06 atm |
| 2 mTorr | 2.63158e-06 atm |
| 3 mTorr | 3.94737e-06 atm |
| 5 mTorr | 6.57895e-06 atm |
| 10 mTorr | 1.31579e-05 atm |
| 20 mTorr | 2.63158e-05 atm |
| 25 mTorr | 3.28947e-05 atm |
| 50 mTorr | 6.57895e-05 atm |
| 75 mTorr | 9.86842e-05 atm |
| 100 mTorr | 0.000131579 atm |
| 250 mTorr | 0.000328947 atm |
| 500 mTorr | 0.000657895 atm |
| 1000 mTorr | 0.00131579 atm |
| 5000 mTorr | 0.00657895 atm |
Exact factor: 1 millitorr = 1.31578947368e-06 atmospheres.
| Quantity | mTorr | atm |
|---|---|---|
| Sea-level air | 7.6e+05 mTorr | 1 atm |
| A car tyre | 1.655e+06 mTorr | 2.177 atm |
| Blood pressure, systolic | 1.2e+05 mTorr | 0.1579 atm |
| A bicycle tyre | 4.654e+06 mTorr | 6.124 atm |
| A domestic water main | 3e+06 mTorr | 3.948 atm |
| A steam boiler | 7.501e+06 mTorr | 9.869 atm |
Published reference values, converted with the same factor this page uses.