ATA to PSI Calculator and Absolute-Pressure Conversion Guide

ATA to PSI is a conversion from atmospheres absolute to pounds per square inch absolute. One atmosphere absolute equals 14.6959487755 psia. Multiply ATA by 14.69594877551345 to convert it; divide psia by the same factor to go back. Check the reference before using any result: psig starts from local atmospheric pressure, not a complete vacuum. This calculator performs a unit conversion, not a chamber operating recommendation. Its four-decimal display is presentation precision, not a claim about measurement accuracy.

Updated September 2026.

ATA to PSI Calculator

The calculator converts ATA to psi absolute, abbreviated psia, and converts psia back to ATA. It keeps the full registered standard-atmosphere factor during the calculation and rounds only the displayed answer to four decimal places. Negative inputs are rejected because this converter is defined for non-negative absolute pressure.

The ultimate source determines the “real” value. A display marked “1.5 ATA” may be a rounded setpoint, a converted gauge reading, or a true absolute-pressure indication. Record the label on your instrument, alongside its listed precision, before comparing this value with chamber documentation, schematics, repair reports, and quotations.

ATA, atm, and “at” Are Not Interchangeable Labels

ATA means atmospheres absolute in the chamber context; atm denotes the standard-atmosphere unit; and “at” denotes the technical atmosphere. ATA and standard atm use the same 101,325-pascal magnitude when the reference is clear, but technical atmosphere is a different unit and must not enter the same formula.

The 3.2% Technical-Atmosphere Check

The dangerous part is not the multiplication. It is assuming that every word resembling “atmosphere” has the same magnitude and zero point. The NIST CODATA standard-atmosphere value is exactly 101,325 Pa. NIST’s pressure table gives a technical atmosphere as 98,066.5 Pa, about 3.2% lower.

Reimers Systems Inc.’s K102831 510(k) summary, hosted in the U.S. Food and Drug Administration’s database, also spells out “atmospheres absolute (ATA)” in a chamber specification. That supports the notation, not a treatment protocol or a recommendation for any pressure level.

The Exact ATA-to-PSIA Formula

For atmospheres to psi on the absolute scale, use psia = ATA × 14.69594877551345. For the reverse direction, use ATA = psia ÷ 14.69594877551345. Keep the full factor during intermediate steps, then round the displayed result to the precision needed for communication. Never treat added decimal places as new measurement certainty.

The factor is traceable through pascals: one ATA uses the exact 101,325 Pa standard atmosphere, while one psi uses 6,894.757293168 Pa in the registry. The NIST pressure-measurement reference prints rounded table values for both units, which agree with this ratio.

Worked example: 1.5 ATA

1. Preserve the source — record the original value as 1.5 ATA and keep its label.
2. Multiply once — 1.5 × 14.69594877551345 = 22.043923163270175 psia.
3. Round for display — show 22.0439 psia in the calculator, while recognizing that the input itself has fewer significant digits.
4. Check the reference — compare only with another absolute-pressure value unless atmospheric pressure has been measured or specified.

In a spreadsheet, the forward formula can be entered as =A2*14.69594877551345. The reverse formula is =B2/14.69594877551345. Keep the source ATA or psia cell in the sheet so an auditor can reproduce the result instead of receiving a detached rounded number.

ATA-to-PSIA Conversion Chart

Using the exact formula above, this chart converts common ATA values to psia. Its gauge-equivalent column is deliberately conditional: it subtracts one standard atmosphere only to illustrate the reference gap. Field comparison with psig must use the applicable local atmospheric pressure and the instrument documentation.

These rows are conversion references, not instructions to select or operate a chamber at any pressure. For pressure-level context, use the separate hyperbaric chamber ATA pressure guide. For model filtering, start with the chambers-by-ATA hub.

PSIA vs PSIG: Run the Pressure-Reference Check First

As the conversion chart shows, psia references a complete vacuum, while psig references atmospheric pressure. Therefore, an ATA value converts directly to psia, but not directly to psig without an atmospheric reference. At standard sea-level pressure, subtracting about 14.6959 produces an illustrative gauge equivalent; local conditions can make that subtraction different.

The U.S. Geological Survey pressure guide defines absolute pressure against vacuum and gauge pressure against atmosphere. The National Oceanic and Atmospheric Administration gives 1013.25 hPa as standard sea-level pressure. A PumpWorks worked example uses 13.91 psia at 1,500 ft, showing why a fixed 14.7 subtraction isn’t universal.

Where the Atmospheric Reference Comes From

Standard atmospheric pressure at sea level is also known as 1 atmosphere. Atmospheric pressure decreases as elevation and height increase because the surrounding air column places less mass above the measurement point. Normal air and weather changes mean the local reference is not constant; barometric pressure changes can occur progressively. In a simplified model, gas density and gravity affect the column. That concept differs from hydrostatic pressure, where a fluid can exert pressure directly proportional to its density, gravity, and depth.

The correct pressure symbol and reference therefore matter whenever you convert atm to psi, standard atmosphere to psi, or atmospheric pressure to psi. At standard atmosphere, the rounded value is 14.7 pounds per square inch, but the psi conversion still has an absolute reference.

This conversion calculator is a unit of pressure tool, not a length, mass, or medical model. It doesn’t convert centimeter, millimeter, or meter values; evaluate tissue or body tissues; report inches of mercury; or set an industrial gas system’s maximum pressure. Those measurements are commonly used elsewhere, but they don’t alter this conversion formula or conversion table.

The PSIA/PSIG Suffix Ledger

For example, 1.5 ATA converts to 22.0439 psia. Subtracting one standard atmosphere gives about 7.3480 psig only under that stated reference. If the actual atmosphere were 13.91 psia, the same 22.0439 psia absolute pressure would correspond to about 8.1339 psig. The zero is changed, not the conversion.

How to Read a Hyperbaric Chamber Pressure Specification

So, to match any given quote, display, and manual, identify the exact unit string, reference condition (for example, relative to local ambient atmospheric pressure), location, chamber model, configuration at the time of testing, and calibration details before comparing numbers or attempting any conversion. A converted value is meaningful only when those details are precisely defined. If some detail is absent, ask the manufacturer or qualified service personnel instead of assuming it.

MACY-PAN’s public model specification comparator lists soft-chamber ranges around 1.3–1.5 ATA and selected 2.0 ATA configurations. These are first-party catalog examples, not independent safety evidence, and exact options can vary. The hard-versus-soft pressure advisor helps separate chamber categories before a quote review.

A Life Support Technologies patent describes separate set-pressure and chamber-pressure needles across a 1–3 ATA range. That is not evidence that every chamber uses the same hardware, but it illustrates an observable distinction: set pressure, indicated actual pressure, and reference pressure can be separate values. Instrumentation trade guidance likewise distinguishes vented gauge transmitters from vacuum-referenced absolute transmitters.

“Follow the manufacturer’s instructions for use for each HBOT device being used.”

An archived copy of the FDA communication calls on health care providers and facilities to follow manufacturer-recommended maintenance intervals and safety checks. If a quotation or display does not expose its reference basis, request the exact model configuration and documentation before relying on a conversion.

Six ATA-to-PSI Mistakes That Change the Meaning

The most serious ATA-to-PSI errors preserve plausible arithmetic while changing the pressure reference, unit magnitude, or operational meaning. Catch them by retaining the source label, converting only like-for-like references, and treating every undocumented “psi” value as incomplete. The following six checks address common specification handoff errors.

1. Bare PSI: the number may be absolute, gauge, or differential.
2. Fixed atmospheric subtraction: 14.7 psi is a rounded standard condition, not every site’s ambient pressure.
3. ATA versus at: standard and technical atmospheres differ by about 3.2%.
4. Early rounding: repeated use of 14.7 compounds avoidable error.
5. Configuration drift: a model family page doesn’t prove the exact quoted option.
6. Operational overreach: a converter can’t validate a setpoint or replace a manual.

For equipment context, compare the soft-shell chamber range with the hard chamber range. Those pages help identify the product class; they don’t change the conversion factor or resolve an undocumented instrument reference.

Frequently Asked Questions

These short answers cover the most common ATA-to-PSI checks: the one-ATA factor, common values, standard-atmosphere rounding, direct psig conversion, and the calculator’s safety boundary. Each answer assumes ATA means standard atmospheres absolute. If the source uses another convention, verify it before calculating.

Need a Pressure Specification Checked Against a Model?

Send the exact model code, unit string, reference basis, site location, and the document or display you’re comparing. A reference mismatch can delay procurement or leave a service comparison unusable, so include the relevant manual page, calibration record, drawing, or quotation as evidence. MACY-PAN can confirm the quoted configuration and point you to the applicable documentation.

Request configuration confirmation