Vacuum Pressure Units — Quick Reference

Unit Conversion Table

Starting Unit	mbar	Pa	Torr	atm	PSI
1 mbar	1	100	0.7501	9.869 × 10⁻⁴	0.01450
1 Pa	0.01	1	7.501 × 10⁻³	9.869 × 10⁻⁶	1.450 × 10⁻⁴
1 Torr	1.333	133.3	1	1.316 × 10⁻³	0.01934
1 atm	1013	101 325	760.0	1	14.70
1 PSI	68.95	6895	51.71	0.06805	1

Quick Conversion Rules

1
1 mbar ≈ 0.75 Torr Quick mental conversion: multiply mbar by ¾
2
1 Pa = 0.01 mbar Move the decimal two places: 100 Pa = 1 mbar
3
1 atm ≈ 1013 mbar (sea level) Standard atmospheric pressure at sea level
4
1 atm ≈ 760 Torr Historical definition: height of a mercury column at 0°C
5
Atmospheric at Selkirk ≈ 950 mbar Elevation 530 m reduces atmospheric pressure by ~6% vs sea level

Selkirk College note: At 530 m elevation, local atmospheric pressure is approximately 950 mbar (≈ 713 Torr, ≈ 95 000 Pa). Always use local atmospheric as your reference when calculating gauge pressure or checking for leaks. Your barometric reference gauge (R1-G-BX) confirms the actual value.