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Convert atmospheres (atm) to pounds per square inch (PSI) instantly with our free online calculator. Essential for HVAC systems, scuba diving calculations, tire pressure monitoring, industrial pressure vessels, and scientific applications.
14.696 PSI
per Atmosphere
101,325 Pa
1 atm in Pascals
29.4 PSI
at 33 ft Depth (Diving)
Formula: PSI = Atmospheres × 14.696
| Atmospheres | PSI | Real-World Context |
|---|---|---|
| 0.5 atm | 7.35 PSI | Low vacuum, HVAC suction line |
| 0.75 atm | 11.02 PSI | High-altitude atmospheric pressure |
| 1.0 atm | 14.70 PSI | Standard sea-level pressure |
| 1.5 atm | 22.04 PSI | Typical car tire pressure |
| 2.0 atm | 29.39 PSI | 33 ft underwater (scuba diving) |
| 2.5 atm | 36.74 PSI | Bicycle tire pressure |
| 3.0 atm | 44.09 PSI | 66 ft underwater depth |
| 4.0 atm | 58.78 PSI | 99 ft underwater depth |
| 5.0 atm | 73.48 PSI | High-pressure HVAC discharge |
| 10 atm | 147.0 PSI | Industrial compressor output |
| 15 atm | 220.4 PSI | High-pressure gas cylinders |
| 20 atm | 293.9 PSI | Commercial HVAC systems |
| 50 atm | 734.8 PSI | Hydraulic systems |
| 100 atm | 1,470 PSI | Industrial pressure vessels |
| 200 atm | 2,939 PSI | Scuba tank full pressure |
An atmosphere (atm) is a unit of pressure defined as exactly 101,325 pascals, which represents the average atmospheric pressure at sea level under standard conditions. The atmosphere is a convenient reference unit in science and engineering because it represents the natural pressure we experience daily on Earth's surface. One atmosphere equals the weight of the entire column of air extending from sea level to the edge of space, pressing down on each square inch of surface area.
Pounds per square inch (PSI) is an imperial unit of pressure commonly used in the United States for measuring tire pressure, hydraulic systems, compressed air, and HVAC equipment. PSI literally means the force in pounds exerted on one square inch of area. The term PSI can refer to gauge pressure (PSIG), which measures pressure relative to atmospheric pressure, or absolute pressure (PSIA), which includes atmospheric pressure in the measurement.
The relationship between these units is precise: 1 atmosphere = 14.696 PSI (often rounded to 14.7 PSI for practical applications). This conversion factor is crucial across numerous industries. In meteorology, atmospheric pressure readings help predict weather patterns. In scuba diving, pressure increases by 1 atm for every 33 feet of depth. In HVAC systems, refrigerant pressures are often specified in both units depending on regional preferences and equipment manufacturers.
Understanding the distinction between gauge and absolute pressure is essential when converting atmospheres to PSI. At sea level, a tire gauge reading 32 PSIG actually contains 46.7 PSIA (32 + 14.7), which equals approximately 3.18 atmospheres of absolute pressure. This distinction matters greatly in scientific calculations, engineering designs, and safety specifications for pressure vessels.
The formula to convert atmospheres to PSI is: PSI = Atmospheres × 14.696. Simply multiply the pressure in atmospheres by the conversion factor 14.696 to obtain the equivalent pressure in pounds per square inch.
Question: A scuba diver reaches a depth where the absolute pressure is 3 atmospheres. What is this pressure in PSI?
Context: This pressure occurs at approximately 66 feet (20 meters) depth in seawater.
Question: An HVAC system's discharge line operates at 5.5 atmospheres. Convert this to PSI for equipment specifications.
Note: This is absolute pressure (PSIA). If converting to gauge pressure, subtract 14.7 to get approximately 66.1 PSIG.
Question: At 10,000 feet elevation, atmospheric pressure is approximately 0.7 atm. What is this in PSI?
Impact: This reduced pressure affects engine performance, cooking times, and tire pressure readings.
For quick estimates, multiply atmospheres by 15 instead of 14.696. This gives results within 2% accuracy and is easy to calculate mentally. For example: 4 atm × 15 = 60 PSI (actual: 58.8 PSI). Another useful shortcut: remember that 2 atm is approximately 30 PSI, which helps when checking scuba diving pressures or tire inflation. These mental estimates work well for field applications where precision calculations aren't critical.
| Depth (feet) | Atmospheres | PSI (Absolute) |
|---|---|---|
| Surface (0) | 1.0 atm | 14.7 PSIA |
| 33 ft (recreational limit) | 2.0 atm | 29.4 PSIA |
| 66 ft | 3.0 atm | 44.1 PSIA |
| 99 ft | 4.0 atm | 58.8 PSIA |
| 130 ft (advanced limit) | 4.94 atm | 72.6 PSIA |
| 165 ft | 6.0 atm | 88.2 PSIA |
| 198 ft | 7.0 atm | 102.9 PSIA |
| Application | Typical PSIG | Atmospheres (Absolute) |
|---|---|---|
| Bicycle tire (road) | 80-130 | 6.4-9.8 atm |
| Bicycle tire (mountain) | 25-40 | 2.7-3.7 atm |
| Car tire (passenger) | 32-35 | 3.2-3.4 atm |
| SUV/truck tire | 35-45 | 3.4-4.1 atm |
| Motorcycle tire | 28-42 | 2.9-3.9 atm |
| RV tire | 50-80 | 4.4-6.4 atm |
| Commercial truck tire | 75-110 | 6.1-8.5 atm |
| Temperature (°F) | PSIG | Atmospheres (Absolute) |
|---|---|---|
| 40°F (suction) | 118 | 9.0 atm |
| 65°F (typical indoor) | 201 | 14.7 atm |
| 75°F (return air) | 234 | 16.9 atm |
| 100°F (outdoor coil) | 340 | 24.1 atm |
| 120°F (discharge) | 457 | 32.1 atm |
Scuba divers must understand pressure conversions to calculate air consumption rates, plan decompression stops, and ensure safe ascent profiles. Pressure increases by 1 atm (14.7 PSI) every 33 feet, affecting how long a diver can stay at depth and how much air they consume. Dive computers and pressure gauges may display readings in different units depending on manufacturer and region.
HVAC technicians use both atmospheres and PSI when working with refrigerant pressures, vacuum pumps, and system diagnostics. Equipment specifications from international manufacturers may use atmospheres, while US field instruments typically display PSI. Accurate pressure conversions ensure proper refrigerant charging, leak detection, and system performance optimization.
Tire pressure recommendations, turbocharger boost levels, and fuel injection systems all rely on precise pressure measurements. Tire pressure monitoring systems (TPMS) alert drivers when pressure drops, affecting fuel economy, tire wear, and safety. Turbocharged engines operate at 1.5-2.5 atmospheres boost, requiring accurate pressure sensors and conversions for engine management systems.
Chemical plants, refineries, and manufacturing facilities use pressure vessels rated in both atmospheres and PSI. Safety codes, pressure relief valves, and operating procedures require precise conversions. A vessel rated for 100 atmospheres (1,470 PSI) must have appropriate safety margins, pressure monitoring, and emergency shutdown systems to prevent catastrophic failures.
Atmospheres typically refer to absolute pressure. If you need gauge pressure (PSIG), subtract 14.7 from your PSIA result. A tire at 2 atm absolute = 29.4 PSIA = 14.7 PSIG.
The exact factor is 14.696, but 14.7 provides accuracy within 0.03% — more than sufficient for tire pressure, diving, and most HVAC applications.
At high altitudes, "1 atmosphere" of local barometric pressure is less than 14.7 PSI. Denver (5,280 ft) has ~12.1 PSI atmospheric pressure, affecting tire gauges and barometers.
1 bar = 14.504 PSI, while 1 atm = 14.696 PSI. The difference is small (1.3%) but matters in scientific work. 1 bar ≈ 0.987 atm.
Tire pressure changes ~1-2 PSI per 10°F. A tire at 32 PSIG when cold may read 35 PSIG after highway driving due to heat buildup. Always measure tire pressure when tires are cold.
For pressure vessel ratings, scuba tank certifications, and HVAC refrigerant limits, maintain at least 3-4 decimal places to ensure adequate safety margins.
One atmosphere equals exactly 14.696 PSI (commonly rounded to 14.7 PSI). This is the pressure exerted by Earth's atmosphere at sea level under standard conditions. This fundamental conversion is widely used in engineering, meteorology, and scientific calculations.
Two atmospheres equals approximately 29.4 PSI (29.392 PSI precisely). This pressure is commonly encountered at 33 feet underwater in scuba diving, where you experience 1 atm from the water column plus 1 atm from the air above, or in pressurized industrial vessels and HVAC systems.
At sea level, the entire column of air above us weighs approximately 14.7 pounds per square inch of surface area. This weight creates the pressure we call one atmosphere. The exact value (14.696 PSI) was determined through precise measurement and international standardization.
Atmospheric pressure decreases with elevation because there is less air above pressing down. At 5,000 feet elevation, atmospheric pressure is about 0.83 atm (12.2 PSI). At 10,000 feet, it drops to approximately 0.69 atm (10.1 PSI). This affects cooking times, engine performance, and tire pressure readings.
PSIG (pounds per square inch gauge) measures pressure relative to atmospheric pressure, while PSIA (pounds per square inch absolute) includes atmospheric pressure in the measurement. At sea level: 0 PSIG = 1 atm = 14.7 PSIA. Most tire pressure gauges read PSIG, while scientific instruments typically measure PSIA.
In scuba diving, pressure increases by 1 atmosphere (14.7 PSI) for every 33 feet (10 meters) of depth in seawater. At 33 feet, divers experience 2 atm total (29.4 PSIA): 1 atm from the water and 1 atm from the air above. This pressure relationship is critical for calculating air consumption, dive tables, and decompression requirements.
HVAC systems typically operate at pressures ranging from 0.5 to 5 atmospheres (7 to 73 PSI) depending on the refrigerant and system design. Low-pressure refrigerants like R-134a operate around 0.3-0.5 atm (5-7 PSIG) on the suction side, while high-pressure refrigerants can reach 15-25 atm (220-370 PSIG) on the discharge side during normal operation.
Tire pressure changes approximately 1-2 PSI (0.07-0.14 atm) for every 10°F temperature change due to the ideal gas law. When tires heat up from driving or ambient temperature increases, air molecules move faster and exert more pressure. This is why tire manufacturers recommend checking tire pressure when tires are cold (before driving) to get accurate readings.
This calculator uses the internationally recognized conversion factor of 1 atmosphere = 14.696 PSI. For safety-critical applications including pressure vessel design, scuba diving equipment, HVAC systems, and industrial processes, always verify pressure conversions with certified instruments and follow applicable safety codes and manufacturer specifications.