Bar to PSI and Litres to Cubic Feet: Dive Unit Converter

A converter for the six kinds of number divers move between metric and imperial: pressure (bar, psi, MPa), volume (litres, cubic feet), depth (meters, feet), temperature (°C, °F, K), weight (kg, lb) and breathing rate (L/min, ft³/min, bar/min). One bar is 14.5038 psi, one meter is 3.28084 feet and one cubic foot is 28.3168 litres.

The formula

1 psi = \frac{0.45359237 \times 9.80665}{{0.0254}^{2} \times 10^{5}} bar 1 ft = 0.3048 m 1 {ft}^{3} = 28.316846592 L

The exact definitions: a pound-force on a square inch, the international foot, and its cube. Every other factor on the page follows from them, plus 1 MPa = 10 bar and 1 lb = 0.45359237 kg.

°F = °C \times 1.8 + 32 K = °C + 273.15 bar/min = \frac{L/min \times 1.01325}{V_{cyl}}

Temperature is offset as well as scaled. A breathing rate in bar/min belongs to one cylinder: V_cyl is its water volume in litres, and 1.01325 bar is the surface reference the litres are counted at.

Worked example

Each line is one conversion, done by the same code the calculator runs.

1A 232 bar fill is 3365 psi (1 bar = 14.5038 psi).
2An AL80's 3000 psi working pressure is 206.8 bar.
3A 40 m depth limit is 131 ft (1 m = 3.28084 ft, a length, not a pressure).
4An SRMV of 20 L/min is 0.71 ft³/min, and on a 12.2 L cylinder it takes 1.66 bar a minute at the surface.

Bar to psi for diving

bar	psi	MPa
50	725	5
100	1450	10
150	2176	15
200	2901	20
207	3002	20.7
232	3365	23.2
250	3626	25
300	4351	30

psi	bar
500	34.5
725	50.0
1000	68.9
1500	103.4
2000	137.9
2400	165.5
3000	206.8
3300	227.5
3442	237.3
4350	299.9

Gauge pressures. 3000 psi is the AL80's working pressure; 3442 psi is the 237 bar of HP steel cylinders.

Meters to feet for diving

m	ft
5	16
10	33
18	59
20	66
30	98
40	131
50	164
60	197
100	328

ft	m
10	3.0
15	4.6
20	6.1
33	10.1
40	12.2
60	18.3
66	20.1
100	30.5
130	39.6
200	61.0

Lengths. The pressure at a depth also depends on the water: 10.00 m of EN 13319 water adds 1 bar, fresh water needs 10.20 m.

Cubic feet and litres for scuba cylinders

A cylinder's litres and its cubic feet are two different quantities. Metric divers name a cylinder by its water volume; US divers name it by the gas it holds at its working pressure. Converting the water volume to cubic feet gives a figure under one: the AL80 problem.

Cylinder	Water volume	Same in ft³	Free gas contained, 15 °C	Rated basis, 70 °F
AL80	11.1 L	0.39 ft³	2204 L	77.4 ft³
HP100	12.9 L	0.46 ft³	2879 L	101.2 ft³
Steel 12L 232	12 L	0.42 ft³	2629 L	92.4 ft³
Steel 15L 232	15 L	0.53 ft³	3286 L	115.4 ft³
AL63	9 L	0.32 ft³	1787 L	62.8 ft³
LP85	13 L	0.46 ft³	2303 L	80.8 ft³
Steel 12L 300	12 L	0.42 ft³	3221 L	113.3 ft³
AL40	5.7 L	0.20 ft³	1132 L	39.7 ft³

All the gas the cylinder contains at its working pressure, real gas expanded to 1 atm: 15 °C is the EN/ISO convention, 70 °F the true-capacity convention of Luxfer's and Faber's HP spec sheets. All 38 cylinders are on scuba cylinder sizes.

SRMV in L/min, ft³/min and bar/min

L/min	ft³/min	bar/min, 12.2 L	psi/min, AL80
10	0.35	0.83	13.2
12	0.42	1.00	15.9
15	0.53	1.25	19.9
18	0.64	1.49	23.8
20	0.71	1.66	26.5
25	0.88	2.08	33.1
30	1.06	2.49	39.7

Surface rates. bar/min and psi/min are the ideal-gas conversion for that cylinder (11.1 L water volume for the AL80).

How Dive Kit computes this

Each conversion is the Dive Kit app's own, from @divekit/core, computed with decimal arithmetic so a value converted there and back returns to what you typed. The result shows at most two decimals; the factor line under it shows six significant digits.

The units here are your choice for each conversion and do not follow the page's metric or imperial setting, the same as in the app, where the converter is a scratchpad that leaves your unit preference alone.

Depth converts as a length. The pressure at a depth also depends on the water: Dive Kit's planners count 1 bar for every 10.00 m of EN 13319 water by default, 10.20 m of fresh water. A breathing rate in bar/min converts to L/min only through a cylinder's water volume, so that mode asks for one; it is the ideal-gas conversion. The SAC and RMV calculator measures both from a real gauge drop instead.

The app screen for this tool is documented in the user guide: Unit Converter in the Dive Kit guide.

How many psi is 200 bar?

Multiply bar by 14.5038, or divide psi by it. The tables above list the fills divers meet most, both ways, computed by the same code as the converter. Watch the AL80: its 3000 psi working pressure is a little over 200 bar.

Why does an AL80 hold 80 cubic feet but only 11 litres?

Because the two numbers measure different things. 11.1 L is the AL80's water volume, the space inside it. 80 cubic feet is the gas it holds at 3000 psi, expanded to the surface. Converting 11.1 L to cubic feet gives less than half a cubic foot, which is why the converter's volume mode is the wrong tool for cylinder sizes: use scuba cylinder sizes.

How do I convert meters of depth to feet?

Multiply by 3.28084 (one foot is exactly 0.3048 m); the table above lists common depth limits. That is the length. For the pressure at a depth, add the water: about one bar per 10 m of sea water on top of the 1.01325 bar at the surface.

How do I convert SAC in bar/min to L/min?

Multiply by the cylinder's water volume and divide by 1.01325. Pick SRMV/SAC in the converter, set bar/min on one side and enter your cylinder's water volume.

Sources

NIST Guide to the SI (SP 811), Appendix B.8: Factors for units listed alphabetically : The conversion factors: psi to pascal, the foot as exactly 0.3048 m, the cubic foot, the pound, the bar as exactly 100,000 Pa, and the Fahrenheit and kelvin formulas.
EN 13319:2000, Diving accessories: depth gauges and combined depth and time measuring devices : The depth-gauge standard that the EN 13319 water setting, Dive Kit's default for pressure at depth, is named after.

Last updated 30 October 2026

Dive Unit Converter