Convert atmospheres to psi

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Enter a value in atmospheres and read the result in psi. At 2 atm the converter shows 29.3919 psi, because one atmosphere is 14.6959 psi.

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What is a standard atmosphere, and what is a psi?

The standard atmosphere describes the pressure air exerts at sea level. Its value is fixed at exactly 101,325 pascals[1], and it is sometimes used as a reference pressure[2].

The symbol of the unit is atm. A separate unit called the technical atmosphere carries the symbol at and equals 98,066.5 pascals[1], which comes to 14.2233 psi. This page works with the standard atmosphere.

A psi is one pound-force spread over one square inch[3]. It equals 6,894.757 pascals[1], so it is a far smaller unit than the atmosphere. That size difference is why a single atmosphere already gives a two-digit figure in psi.

Pressure gauge with a white dial graduated from 0 to 4 and the word bar below it, mounted on a pipe wrapped in silver foil next to black insulation
This dial runs from 0 to 4 and carries the word bar, with the needle standing between 1 and 2. Bar and atmosphere turn the same number into different psi: two bar come to 29.0075 psi, while two atmospheres come to 29.3919 psi. Photo: Fabian Kleiser, Unsplash.

How many psi are in one atmosphere?

One atmosphere is 14.6959 psi. You multiply the number of atmospheres by that value, so the formula reads psi = atm × 14.6959.

The figure comes from dividing two definitions by each other. An atmosphere is exactly 101,325 pascals and a psi is 6,894.757 pascals[1]. That psi figure is rounded, and dividing the full definitions gives 14.695 948 8. The IUPAC pressure conversion table prints the same number[4].

Technical texts also use the rounded 14.7 psi per atmosphere. Rounding shifts the result by 0.004 psi for every atmosphere. At two hundred atmospheres that adds up to 0.81 psi. The converter on this page uses the full factor, so its result matches the table to the fourth decimal place.

The same factor works across the whole range. One tenth of an atmosphere gives 1.4696 psi, and a thousand atmospheres give 14,695.9488 psi.

How do you convert atm to psi? Formula and example

The arithmetic takes one step: multiply the number of atmospheres by 14.6959. Three worked examples follow.

Two and a half atmospheres give 36.7399 psi. Five atmospheres come to 73.4797 psi. A hundred atmospheres reach 1,469.5949 psi. The same multiplication produces all three, because the relation between the units is linear.

The psi to atm converter runs the calculation the other way. If your reading is in bar or in kilopascals, the bar to psi converter and the kPa to psi converter handle those.

How many psi is a given number of atmospheres?

The first column gives the result in psi and the second gives the same pressure in kilopascals, the SI unit. The row with one atmosphere is the starting point for every other row.
AtmospheresPsiKilopascals
0.1 atm1.4696 psi10.1325 kPa
0.2 atm2.9392 psi20.265 kPa
0.3 atm4.4088 psi30.3975 kPa
0.5 atm7.348 psi50.6625 kPa
0.8 atm11.7568 psi81.06 kPa
1 atm14.6959 psi101.325 kPa
1.2 atm17.6351 psi121.59 kPa
1.3 atm19.1047 psi131.7225 kPa
1.5 atm22.0439 psi151.9875 kPa
1.8 atm26.4527 psi182.385 kPa
2 atm29.3919 psi202.65 kPa
2.2 atm32.3311 psi222.915 kPa
2.5 atm36.7399 psi253.3125 kPa
2.8 atm41.1487 psi283.71 kPa
3 atm44.0878 psi303.975 kPa
3.5 atm51.4358 psi354.6375 kPa
4 atm58.7838 psi405.3 kPa
4.5 atm66.1318 psi455.9625 kPa
5 atm73.4797 psi506.625 kPa
6 atm88.1757 psi607.95 kPa
7 atm102.8716 psi709.275 kPa
8 atm117.5676 psi810.6 kPa
9 atm132.2635 psi911.925 kPa
10 atm146.9595 psi1,013.25 kPa
12 atm176.3514 psi1,215.9 kPa
14 atm205.7433 psi1,418.55 kPa
16 atm235.1352 psi1,621.2 kPa
18 atm264.5271 psi1,823.85 kPa
20 atm293.919 psi2,026.5 kPa
25 atm367.3987 psi2,533.125 kPa
29 atm426.1825 psi2,938.425 kPa
30 atm440.8785 psi3,039.75 kPa
35 atm514.3582 psi3,546.375 kPa
40 atm587.838 psi4,053 kPa
45 atm661.3177 psi4,559.625 kPa
50 atm734.7974 psi5,066.25 kPa
60 atm881.7569 psi6,079.5 kPa
70 atm1,028.7164 psi7,092.75 kPa
71 atm1,043.4124 psi7,194.075 kPa
80 atm1,175.6759 psi8,106 kPa
90 atm1,322.6354 psi9,119.25 kPa
100 atm1,469.5949 psi10,132.5 kPa
150 atm2,204.3923 psi15,198.75 kPa
200 atm2,939.1898 psi20,265 kPa
250 atm3,673.9872 psi25,331.25 kPa
300 atm4,408.7846 psi30,397.5 kPa
380 atm5,584.4605 psi38,503.5 kPa
400 atm5,878.3795 psi40,530 kPa
500 atm7,347.9744 psi50,662.5 kPa
700 atm10,287.1641 psi70,927.5 kPa
1,000 atm14,695.9488 psi101,325 kPa
A hundred atmospheres come to 1,469.5949 psi and 10,132.5 kilopascals. The relation is linear, so ten times the atmospheres gives ten times the psi.

How much psi does a given depth produce?

NOAA Diving Center material puts one atmosphere at 33 feet of sea water and 34 feet of fresh water[5]. A lake therefore reaches the same number of atmospheres slightly deeper than the sea. The psi column gives absolute pressure, so it includes the atmosphere of air above the surface.
Absolute pressureDepth in sea waterDepth in fresh waterPsi
1 ATA0 ft0 ft14.6959 psi
2 ATA33 ft34 ft29.3919 psi
3 ATA66 ft68 ft44.0878 psi
4 ATA99 ft102 ft58.7838 psi
5 ATA132 ft136 ft73.4797 psi
6 ATA165 ft170 ft88.1757 psi
10 ATA297 ft306 ft146.9595 psi
40 ATA1,287 ft1,326 ft587.838 psi
Two atmospheres absolute arrive at 33 feet of sea water and 34 feet of fresh water. Forty atmospheres come only at 1,287 feet.

How much psi is the pressure in a hyperbaric chamber?

A hyperbaric chamber is a sealed room where staff raise the air pressure while the patient breathes pure oxygen through a mask. The chamber run by Hyperbaric Treatment & Training Services in Birkenhead is pressurised to 2.4 atmospheres absolute, the equivalent of 14 metres of seawater, and each session lasts 90 minutes at that depth[6]. Absolute means the figure includes the air pressure around us, so the count starts at one atmosphere.

Converted, 2.4 atmospheres absolute is 35.2703 psi. A gauge that reads zero at room pressure shows 1.4 atmospheres over that, which is 20.5743 psi. In psi the absolute figure is written psia and the gauge figure psig, so the same chamber runs at 35.2703 psia or 20.5743 psig.

What is one atmosphere in other units?

The values come from the IUPAC pressure conversion table[4], and the technical atmosphere from the NIST table[1]. The list shows why bar and atmosphere give two different numbers: 1,325 pascals separate them.
UnitValue of one atmosphere
Pascal (Pa)101,325 Pa
Kilopascal (kPa)101.325 kPa
Bar1.01325 bar
Torr760 Torr
Millimetre of mercury (mmHg)760 mmHg
Technical atmosphere (at)1.033227 at
Pound per square inch (psi)14.6959 psi
The torr is defined as 1/760 of an atmosphere, while the millimetre of mercury comes from the density of mercury and standard gravity. The millimetre of mercury is larger than the torr by 0.000014%, so one atmosphere is exactly 760 torr and 759.9999 mmHg, which also rounds to 760.

Which number formats does this converter accept?

The table shows what the field does with the ways a pressure usually reaches it from dive tables, manuals and spreadsheets. The converter itself calculated every result.
What you typeWhat the converter showsNote
229.3919 psiA plain number is read as atmospheres, because that’s what the field is labeled.
2 atm29.3919 psiThe atm symbol pasted along with the number is skipped, so only the number counts.
2 atmospheres29.3919 psiThe whole word is skipped the same way, so a phrase copied from a text needs no tidying.
2 ATA29.3919 psiThe ATA suffix from dive tables and hyperbaric chamber notes is skipped, and the number counts as absolute atmospheres.
2.536.7399 psiThe period is your decimal point, and that’s exactly how we read it.
2,536.7399 psiA comma with fewer than three digits after it is a decimal comma from a European document, so we read two and a half atmospheres.
1.50022.0439 psiA single period is always read as a decimal point, so the field takes one and a half atmospheres. A note under the field says: Read as 1.5. If you meant 1500, type 1500.
1,50022043.9232 psiA comma followed by three digits groups thousands, so the field reads fifteen hundred atmospheres. A note under the field says: Read as 1500. If you meant 1.5, type 1.5.
1/27.348 psiA fraction with a slash is worked out for you, so half an atmosphere doesn’t need to become 0.5 first.
2½36.7399 psiThe ½ character copied from a text is added to the number in front of it.
-0.5-7.348 psiA minus sign is accepted, so a vacuum gauge reading below the surrounding air pressure converts too.
-80 kPa-11.603 psiA pressure in another unit is converted by the field itself, minus sign included, as long as the minus sits right against the number.
- 80 kPaThe result field stays empty.A minus separated by a space isn’t joined to the number, so nothing is calculated. Type the minus right before the digit.

How do you convert atm to psi in a spreadsheet?

Excel carries a built-in function for pressure units, and the unit codes atm and psi are all it needs.

  1. Type the pressure in atmospheres

    Put the number of atmospheres in a cell, for example 2.5 in cell A2.

  2. Call the CONVERT function

    In the next cell type =CONVERT(A2,"atm","psi"). The function takes number, from_unit and to_unit[7].

  3. Keep the quotation marks on the codes

    The codes "atm" and "psi" stay inside quotation marks and in lower case, because Excel reads them as pressure unit codes.

  4. Drag the formula down

    Grab the bottom right corner of the result cell and drag it along the column to convert a whole list of pressures at once.

Convert other units to Pounds per square inch (psi)

bar to psikPa to psi

Sources

  1. NIST Guide to the SI, Appendix B.9: Factors for Units Listed by Kind of Quantity or Field of Science — National Institute of Standards and Technology
  2. Standard atmosphere (unit) — Wikipedia
  3. Pound per square inch — Wikipedia
  4. Quantities, Units and Symbols in Physical Chemistry (Green Book), 3rd edition, p. 233 — International Union of Pure and Applied Chemistry
  5. Atmospheric and Hydrostatic Pressure — NOAA Diving Center
  6. Our patients — Hyperbaric Treatment & Training Services
  7. CONVERT function — Microsoft

Every figure in the tables was computed from the unit definitions and checked arithmetically before publication. Historical values and the names of local units come from the sources listed above.

Content last reviewed: · written and checked by the Arteon team

Frequently asked questions about converting atm to psi

Is 14.7 psi exactly one atmosphere?

One atmosphere is 14.6959 psi. A reading of 14.7 psi works out to 1.000276 atmospheres, so the gap stays under three ten-thousandths of an atmosphere and workshop arithmetic lands on the same answer.

How many psi are 2 atm?

Two atmospheres come to 29.3919 psi, or 202.65 kilopascals. That is the absolute pressure 33 feet below the surface of the sea.

How many psi is 2.5 atm?

Two and a half atmospheres give 36.7399 psi. In bar the same pressure reads 2.5331, because a bar is a slightly smaller unit than an atmosphere.

How many psi are 10 atm?

Ten atmospheres come to 146.9595 psi and 1,013.25 kilopascals. Absolute pressure reaches that level 297 feet below the surface of the sea.

How many psi are 100 atm?

A hundred atmospheres come to 1,469.5949 psi. In kilopascals that is 10,132.5, exactly one hundred times the value of a single atmosphere.

Is 1 bar 14.5 or 14.7 psi?

One bar is 14.5038 psi and one atmosphere is 14.6959 psi. A bar is exactly 100,000 pascals and an atmosphere is 101,325, so both figures are right, each for its own unit. The bar to psi converter handles bar readings.

What is the difference between the standard and the technical atmosphere?

The standard atmosphere is 101,325 pascals and 14.6959 psi, while the technical atmosphere is 98,066.5 pascals and 14.2233 psi. The second one matches one kilogram-force per square centimetre and carries its own symbol, at.

Is air pressure always one atmosphere?

The standard atmosphere is an agreed value, while real air pressure moves with the weather and with altitude. The records for sea-level air pressure are listed in a table on the psi to atm converter page.

How many atmospheres are 33 feet under water?

Thirty-three feet of sea water add one atmosphere of gauge pressure, so together with the air above the surface that makes two atmospheres absolute. In fresh water the same atmosphere arrives at 34 feet.

Is the atmosphere an SI unit?

The SI unit of pressure is the pascal. The atmosphere is outside the SI, and chemistry has used 100 kilopascals, one bar, as its standard pressure since 1982.

Arteon free tool screenshot: Convert atmospheres to psi

Have a question or a suggestion?

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