How this instrument works
Pressure gauges almost never read from a true vacuum. A tyre gauge, a compressor dial, a process-plant transmitter — nearly all of them are zeroed against the surrounding air, so a reading of 0 on the dial means “the same as atmospheric pressure,” not “no pressure at all.” That zeroed-to-air convention is called gauge pressure, and it's what a bar figure normally means unless someone specifically says otherwise. Absolute pressure, by contrast, is zeroed against a true vacuum, so it always reads atmospheric pressure or higher under ordinary conditions at Earth's surface, never zero.
Converting a gauge bar reading into an absolute psi figure therefore takes two separate steps, not one. First, the unit itself gets rescaled: multiplying by 14.503773773 turns a bar figure into the equivalent number of psi, still measured on the same gauge, atmosphere-zeroed scale. Second, standard atmospheric pressure at sea level — fixed at 14.696 psi — gets added on top, shifting the zero point from “same as the surrounding air” to “true vacuum.” That second step is an addition, not a multiplication, which is the detail that trips up anyone assuming every pressure conversion is a single multiply-through factor.
This calculator's output field is labelled PSIG (psi, absolute) in the tool itself — a label that keeps the familiar gauge abbreviation while flagging, in parentheses, that the number it actually reports has already had that atmospheric offset folded in. Read it as an absolute pressure: the figure you'd see on a dead-weight tester or an absolute-reference transducer measuring the same physical pressure your bar gauge is reading.
- Type your gauge reading, in bar, into the Bar (bar) field, which opens at 2 — a moderate compressed-air or hydraulic gauge pressure.
- Read the result on the PSIG (psi, absolute) line: despite the gauge-style label, this number already has standard atmospheric pressure added in, so it's an absolute reading.
- To recover the plain gauge-psi figure instead, subtract 14.696 from the result, or multiply your bar value by 14.503773773 on its own.
- Confirm your source pressure is genuinely gauge, not already absolute — feeding an absolute bar reading through this page would double-count the atmospheric offset.
Worked example — a 2 bar gauge compressor reading
A compressed-air line reads 2 bar on its gauge, a typical shop-air setting. Enter 2 into Bar (bar) and PSIG (psi, absolute) returns 43.703547546: multiplying 2 by 14.503773773 first gives 29.007547546 psi on the gauge scale, and adding the 14.696 psi atmospheric offset lifts that to 43.703547546 psi absolute.
The offset never disappears, even at zero. A gauge reading of exactly 1 bar converts to 29.199773773 psi absolute, and a gauge reading of 0 bar — meaning no pressure differential from the surrounding air at all — still returns 14.696 psi absolute, because that's what standard atmosphere alone weighs in at on this scale.
Questions
Why does this converter add a number instead of just multiplying?
Because it's bridging two different pressure zero-points, not just two different pressure units. Multiplying by 14.503773773 alone rescales bar into psi while keeping the same gauge, atmosphere-zeroed reference — that part is a pure unit conversion. Shifting from gauge to absolute additionally requires adding standard atmospheric pressure, 14.696 psi, because absolute pressure is measured from a true vacuum, a genuinely different starting point that no multiplication alone can reach.
Why is the output field called PSIG if the number is absolute?
It's a label worth reading carefully. This tool's result field is titled PSIG (psi, absolute) — the parenthetical is the important part, since the figure it reports has already had the 14.696 psi atmospheric offset added, making it a true absolute-pressure value rather than a gauge one. If you need the plain gauge-psi figure instead, subtract 14.696 from the displayed result, or use bar × 14.503773773 on its own.
What is standard atmospheric pressure, and why 14.696 psi specifically?
Standard atmospheric pressure at sea level is defined as 101,325 pascals exactly, a reference value fixed by international convention rather than measured on any given day — real weather pushes the actual air pressure above or below it constantly. Converted into psi, 101,325 Pa works out to about 14.6959 psi, rounded here to 14.696, which is the conventional additive offset used throughout gauge-to-absolute pressure work.
Does the 14.503773773 multiplier ever change?
No — it's fixed by the exact definitions of the bar (100,000 pascals) and the psi (6894.757293168… pascals derived from the pound-force and the inch), so their ratio never varies. What can vary from one job site to another is atmospheric pressure itself, which drifts with weather and altitude; this calculator uses the standard sea-level value of 14.696 psi rather than a live local reading.
My gauge already shows an absolute reading — can I still use this page?
Not directly, or you'll double up the atmospheric offset. This calculator assumes your bar input is a gauge reading, zeroed against the surrounding air, and adds atmospheric pressure on top to reach an absolute figure. If your instrument already reports absolute pressure, convert it with the plain bar-to-psi multiplier — 14.503773773, no addition — instead of this page.
Does altitude change the 14.696 psi offset?
In reality, yes — atmospheric pressure falls with altitude, down to roughly 12.2 psi at 5,000 feet and about 10.1 psi at 10,000 feet, so a gauge-to-absolute conversion done at altitude with the sea-level constant will be off by that much. This calculator always uses the fixed sea-level standard, 14.696 psi, which is the right choice for equipment specified and calibrated at sea-level reference conditions, but not for precise work done well above it.