Tire Pressure: Why It Matters
Underinflated tires waste fuel and wear unevenly. Overinflated tires reduce grip. Check monthly!
Car
30-35 PSI
2.0-2.4 bar
SUV/Truck
32-40 PSI
2.2-2.8 bar
Bicycle
80-130 PSI
5.5-9.0 bar
Soccer Ball
8.5-15.6 PSI
0.6-1.1 bar
Pressure Increases with Depth 🌊
Every 10 meters (33 feet) of water adds 1 atmosphere of pressure.
| Depth | Pressure (ATM) | PSI | Bar |
|---|---|---|---|
| 🏖️ Sea Level | 1 ATM | 14.7 | 1.01 |
| 🏊 10m (33 ft) | 2 ATM | 29.4 | 2.02 |
| 🤿 40m (131 ft) | 5 ATM | 73.5 | 5.07 |
| 🚢 Titanic Wreck | 400+ ATM | 5,880 | 405 |
Pressure conversion formula
Pressure converts linearly once the reference unit is defined. One standard atmosphere equals exactly 101,325 pascals and approximately 14.6959 pounds per square inch.
p_{target} = p_{source} \times f_{source\to target}
pPressure
fPressure conversion factor
Worked conversion example
1
Start with 2 atm
Use pascals per standard atmosphere.
2 × 101,325
2
Calculate
That is 202.65 kilopascals.
= 202,650 Pa
3
Convert to psi
Small rounding differences reflect displayed factor precision.
2 × 14.6959 ≈ 29.39 psi
Frequently Asked Questions
How do I convert PSI to bar?
To convert PSI (pounds per square inch) to bar, divide by 14.504. For example: 35 PSI ÷ 14.504 = 2.41 bar. To convert bar to PSI, multiply by 14.504. Quick reference: 1 bar = 14.504 PSI, and 1 PSI = 0.0689 bar.
What is a pascal and how does it relate to PSI?
The pascal (Pa) is the SI unit of pressure, defined as 1 newton per square meter (N/m²). It's a very small unit: 1 PSI = 6,894.76 pascals. To avoid large numbers, kilopascals (kPa) are often used: 1 PSI = 6.895 kPa, and 1 bar = 100 kPa.
What is atmospheric pressure at sea level?
Standard atmospheric pressure at sea level is 1 atm = 101,325 pascals = 14.696 PSI = 1.01325 bar. This is the weight of Earth's atmosphere pressing down. Pressure decreases as altitude increases—at 5,500m (18,000 ft), it's roughly half.
What pressure should car tires be?
Most passenger car tires should be inflated to 30-35 PSI (2.0-2.4 bar) when cold. Check your door jamb sticker for the exact specification. Underinflated tires increase fuel consumption by up to 3% and wear unevenly. Overinflated tires reduce grip and cause harsh ride quality.