ATA to Bar Calculator: Convert Absolute Pressure

An ATA to bar calculator is a conversion tool for absolute pressure, using the exact identity 1 ATA = 1.01325 bar absolute, written bar(a). To convert ATA to bar(a), multiply the ATA value by 1.01325. To convert bar(a) to ATA, divide by 1.01325. Here, ATA means “atmospheres absolute,” the pressure notation used for hyperbaric chambers.

Atmosphere absolute to bar absolute converter Instant

Value

From ATA · atmosphere absolute bar(a) · bar absolute

⇅

To ATA · atmosphere absolute bar(a) · bar absolute

Result

1.519875

bar(a)

1.5 ATA = 1.519875 bar(a)

ATA and atm use the same 101325 Pa scale, but ATA explicitly denotes absolute pressure. The technical atmosphere at is 98066.5 Pa; bar(a) is absolute pressure, while barg is gauge pressure. Omitting that reference can introduce an error of roughly one atmosphere.

Enter a non-negative value, choose ATA or bar(a), and convert in either direction. Its calculation uses the registered pascal definitions and rounds only the displayed answer to six decimal places.

ATA to Bar Conversion Table

Use this table for a fast pressure conversion. Each value in bar is an absolute pressure, not gauge pressure. Buyers comparing supplier specifications can get the wrong reference when a 1.3 ATA label is copied into a barg column; that mismatch can survive because the numbers still look plausible. NIST’s 101,325 Pa and 100,000 Pa definitions keep every row on one documented basis. The 1.3, 1.5, and 2.0 ATA rows match the pressure tiers shown across MACY-PAN’s public chamber range.

Atmospheres absolute (ATA)	Bar absolute, bar(a)	Reference
0.5	0.506625	Half an atmosphere absolute
1	1.013250	Standard-atmosphere scale
1.3	1.317225	MACY-PAN pressure tier
1.5	1.519875	MACY-PAN pressure tier
2	2.026500	MACY-PAN pressure tier
2.5	2.533125	Worked conversion value
3	3.039750	Three atmospheres absolute

ATA to Bar Formula and Worked Examples

Both units are references to the same physical quantity, so the formula is brief. NIST lists one standard atmosphere as 101,325 pascals and one bar as 100,000 pascals. In hyperbaric device language, an FDA-hosted 510(k) summary submitted by Reimers Systems Inc. uses “atmospheres absolute” with the abbreviation ATA. By dividing the two registered values, we obtain the exact conversion factor. The overall risk exists when an engineering buyer rounds first or copies a gauge-pressure value into an absolute-pressure field; either mistake can shift a 2.0 ATA specification.

FDA device documentation uses the paired wording “atmospheres absolute” and “ATA.” That label is the reason this calculator returns bar(a), not barg.

Example: convert 1.5 ATA to bar. Multiply 1.5 by 1.01325. You get 1.519875 bar(a). For the reverse direction, 1.5 bar(a) divided by 1.01325 equals approximately 1.480385 ATA.

Full registry precision remains in the operation, with rounding applied once at the end. That matters when a clinic, equipment supplier, or procurement team copies a value into a specification table or compares it with a pressure instrument that displays fewer decimal places. Consider a display showing 2.03 bar(a): it may be a rounded representation of 2.0 ATA, not a different conversion rule.

ATA, ATM, AT, Bar(a), and Barg Are Not Interchangeable

Letters surrounding a pressure unit indicate which conversion is appropriate for display on the page. Search results for “ATA to bar” frequently combine three atmosphere labels with two bar references. Such ambiguity presents a genuine procurement risk: a supplier can print 2.0 at while a buyer interprets 2.0 ATA, even though those two values don’t match. Before converting pressure, use this ATA-Bar Basis Lock:

1. Identify the atmosphere label. In the hyperbaric context, ATA means atmospheres absolute. Lowercase atm is the standard-atmosphere unit. Its numeric scale is the same 101,325 Pa, but ATA explicitly tells you the value is absolute pressure.
2. Reject technical atmosphere when the source says ATA. The technical atmosphere uses the symbol at and equals 98,066.5 Pa, or 0.980665 bar. Substituting that factor for ATA makes the answer wrong.
3. Confirm the bar reference. Bar(a), sometimes written bara, is absolute. Barg is gauge pressure relative to the local atmosphere. A universal ATA-to-barg shortcut is impossible without the local atmospheric pressure.

This distinction explains why a generic bar to atm converter may return a plausible number yet still leave an engineering question unanswered. A value in bar needs a reference. NIST supplies the unit definitions, while the Reimers 510(k) summary and a StatPearls chapter hosted in NCBI Bookshelf use the absolute-pressure notation. For an equipment audit, purchase order, or clinic comparison, retaining both the source label and converted value is safer than replacing one with the other.

Using the Conversion With Hyperbaric Chamber Pressure Labels

MACY-PAN groups its public chamber range around 1.3, 1.5, and 2.0 ATA labels. Converting those labels to 1.317225, 1.519875, and 2.0265 bar(a) can help a buyer normalize specifications from suppliers that use different pressure units. The risk is a mismatch between source and reference because a bare bar value may mean absolute or gauge pressure. NIST’s factors resolve the unit conversion; they don’t decide which pressure or model fits a person, clinic, or protocol.

For product comparison, keep the original ATA label beside the converted value. Next, check the rest of the specification separately: chamber construction, stated working pressure, pressure-control method, occupancy, documentation, installation requirements, and intended use. Oxygen concentration and oxygen delivery are also separate from chamber pressure. A number in ATA doesn’t, by itself, establish an oxygen dose.

When comparing pressure tiers rather than converting a single unit, continue to the MACY-PAN chambers-by-pressure overview. For a structured model comparison, use the pressure and model selector. MACY-PAN’s ATA pressure buyer guide provides additional context. Those pages own selection intent; this calculator owns the unit conversion.

Frequently Asked Questions About ATA to Bar

Is 1 bar equal to 1 ATA?

No. One ATA equals 1.01325 bar(a), while one bar(a) equals approximately 0.986923 ATA. Rough rounding can hide the difference, but the units aren’t identical. On a casual display both may appear near 1.0; an engineering specification should retain the source unit and the pressure reference so a reviewer can reproduce the conversion.

How many bar is 2 ATA?

Two ATA equals exactly 2.0265 bar(a). The calculator may display 2.026500 because its output is set to six decimal places, but those trailing zeros don’t change the pressure. Keep the bar(a) label attached so the result isn’t mistaken for gauge pressure.

How do I convert bar to ATA?

Divide the value in bar(a) by 1.01325. For example, 2 bar(a) equals approximately 1.973847 ATA. Before calculating, verify that the source is bar absolute rather than barg. Gauge pressure uses local atmospheric pressure as its reference, so a bare bar value from a gauge or specification can’t safely be treated as bar(a) without checking the label, device documentation, and measurement context.

Is ATA the same as atm?

Both use the same standard-atmosphere scale of 101,325 Pa. ATA explicitly communicates absolute pressure in hyperbaric and diving contexts, while lowercase atm names the standard-atmosphere unit without spelling out that reference in the label. The numerical factor is the same, but the notation carries useful engineering context.

Is ATA the same as the technical atmosphere, at?

No. One technical atmosphere, at, equals 0.980665 bar, while one atmosphere absolute, ATA, equals 1.01325 bar(a). The two labels differ by more than typography: they use different pascal values. A converter built for technical atmosphere will return the wrong result for an ATA chamber label, and the gap becomes larger as the pressure value increases. Check whether the source says ATA, atm, or at before using any factor.

Can ATA be converted directly to barg?

Not with one universal factor. ATA is absolute pressure, while barg is gauge pressure relative to the local atmosphere. Local atmospheric pressure changes with altitude and weather, so it must be known before subtracting it from bar(a). When only ATA is supplied, this calculator can provide bar(a); a separate local-atmosphere input is required for barg.

References & Sources

• NIST Guide to the SI, Chapter 5: standard-atmosphere and bar definitions.
• FDA-hosted 510(k) K102831 summary submitted by Reimers Systems Inc.: use of atmospheres absolute and ATA in the applicant’s device description.
• StatPearls Hyperbaric Physics chapter hosted in NCBI Bookshelf: absolute-pressure terminology and ATA/bar(a) notation.
• BIPM SI Brochure: international SI context for the pascal used as the common conversion base.
• BIPM Resolution 4 of the 10th CGPM: independent confirmation that one standard atmosphere is 101,325 Pa.
• NIST Guide to the SI, Appendix B: conversion-factor table confirming that one standard atmosphere is exactly 101,325 Pa.
• MACY-PAN chambers by pressure: current 1.3, 1.5, and 2.0 ATA tiers.

Need to compare chamber specifications after converting the pressure? Send MACY-PAN the source pressure unit, intended setting, occupancy, and installation requirements for a documented model comparison.