Last updated: May 2026
Convert between PSI, bar, kPa, atm, mmHg, inHg, and torr — for tires, weather, blood pressure, and engineering.
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Pressure is force per unit area, and humans have come up with a remarkable number of ways to measure it — mostly by accident of history. Doctors settled on millimeters of mercury because early blood pressure cuffs used actual mercury columns. Meteorologists use hectopascals or millibars because those numbers feel right for weather maps. Engineers in the US use PSI because imperial units, obviously. Europeans use bar. And scientists use pascals because SI units are tidy and sensible, but 101,325 of them per atmosphere is a little awkward for everyday conversation.
The result: a tire pressure sticker says "220 kPa," a European rental car manual says "2.2 bar," your US gauge reads PSI, and you're standing in a parking lot doing mental math. That's what this converter is for.
Most passenger cars run between 30–36 PSI (207–248 kPa, or 2.07–2.48 bar). The specific number for your car lives on a sticker inside the driver-side door jamb — not on the tire sidewall (that's the maximum, not the recommended). Underinflated tires wear unevenly, reduce fuel economy, and handle sloppily. Overinflated tires give a harsher ride and less contact patch. Both are bad. Check cold — before you've driven more than a mile — for an accurate reading.
Bicycle tires run much higher: road bike tires typically 90–130 PSI (621–896 kPa), mountain bikes 25–35 PSI, and fat bikes can go as low as 5–10 PSI for snow and sand traction. The range is enormous compared to car tires.
Blood pressure is measured in millimeters of mercury (mmHg), a unit that dates to the 1800s when instruments literally used a mercury column. A reading of 120/80 mmHg is considered normal. The top number (systolic) is the pressure when your heart contracts; the bottom (diastolic) is the resting pressure between beats. Converted to more familiar engineering units, 120 mmHg is about 2.32 PSI or 16 kPa — which puts into perspective just how low the pressure is that's keeping you alive.
High blood pressure (hypertension) is defined at 130/80 mmHg or above. Stage 2 hypertension starts at 140/90. A hypertensive crisis — call 911 territory — is over 180/120 mmHg.
Meteorologists measure atmospheric pressure in hectopascals (hPa) or millibars (mbar) — they're the same unit. Standard sea-level pressure is 1013.25 hPa. "High pressure" on weather maps means above ~1020 hPa, typically associated with clear skies. "Low pressure" below ~1000 hPa usually means clouds, storms, and your barometric headache.
Pressure drops with altitude at roughly 1.2 hPa per 10 meters near sea level. Denver at 5,280 ft (1,609 m) sits around 840 hPa. At 18,000 ft (~5,500 m), pressure is about half of sea level — which is why aircraft cabins are pressurized. At Everest's summit, pressure is roughly 337 hPa, or 33% of sea level: every breath contains one-third the oxygen you'd get at the beach.
The Instant Pot and most electric pressure cookers operate at about 10.2–11.6 PSI gauge pressure (0.7–0.8 bar gauge), which translates to roughly 15–16.7 PSI absolute. Stovetop pressure cookers can reach 15 PSI gauge (103 kPa gauge) — the classic "15 PSI" pressure cookers. The higher pressure raises the boiling point of water to about 121°C (250°F) instead of 100°C, which is why they cook food faster. The conversion that matters: 1 bar ≈ 14.5 PSI, and 15 PSI ≈ 1.03 bar.
Every 10 meters (33 feet) of seawater depth adds roughly 1 atm (14.7 PSI / 101.3 kPa) of pressure. At 10 m you're at 2 atm absolute. At 40 m (recreational diving limit) you're at 5 atm — about 73.5 PSI. Scuba tanks are typically filled to 200–300 bar (2,900–4,350 PSI). A full 300-bar tank holds enough compressed air for a dive; when the gauge reads 50 bar (725 PSI) it's time to surface. The nitrogen narcosis that gives divers "the martini effect" kicks in around 30 m because dissolved nitrogen at high partial pressure affects the nervous system.
| Scenario | PSI | bar | kPa | atm | mmHg |
|---|---|---|---|---|---|
| Sea level atmosphere | 14.696 | 1.013 | 101.3 | 1.000 | 760.0 |
| Car tire (typical) | 32.0 | 2.207 | 220.6 | 2.177 | 1,655 |
| Car tire (max / SUV) | 51.0 | 3.516 | 351.6 | 3.470 | 2,637 |
| Road bike tire | 100.0 | 6.895 | 689.5 | 6.805 | 5,171 |
| Normal blood pressure (systolic) | 2.32 | 0.160 | 16.0 | 0.158 | 120.0 |
| Normal blood pressure (diastolic) | 1.54 | 0.107 | 10.7 | 0.105 | 80.0 |
| Pressure cooker (stovetop, gauge) | 15.0 | 1.034 | 103.4 | 1.021 | 776 |
| Instant Pot (high, gauge) | 11.6 | 0.800 | 80.0 | 0.790 | 600 |
| Scuba tank (full, 200 bar) | 2,901 | 200.0 | 20,000 | 197.4 | 150,000 |
| Denver, CO atmosphere | 12.15 | 0.838 | 83.8 | 0.827 | 629 |
All pressure conversions use the pascal (Pa) as the SI base unit. Every unit has a fixed ratio to Pa:
1 PSI = 6,894.76 Pa · 1 bar = 100,000 Pa · 1 kPa = 1,000 Pa · 1 MPa = 1,000,000 Pa · 1 atm = 101,325 Pa · 1 mmHg = 133.322 Pa · 1 inHg = 3,386.39 Pa
To convert any unit to any other: first convert to Pa by multiplying by the "to Pa" factor, then divide by the "to Pa" factor of the target unit. The calculator above does this in real time — change any field and everything else recalculates instantly.
Note on gauge vs absolute pressure: These conversions assume absolute pressure (measured from true zero). Tire gauges and most industrial gauges display gauge pressure — pressure above atmospheric (14.696 PSI). If your gauge reads 32 PSI, the absolute pressure in your tire is approximately 32 + 14.7 = 46.7 PSI absolute.
Most passenger cars recommend 32–35 PSI. The definitive answer is on a sticker inside your driver-side door jamb (or in the owner's manual). Do not use the number on the tire sidewall — that's the maximum safe pressure, not the recommended operating pressure. Always check tires when cold, meaning before you've driven more than a mile. For every 10°F drop in temperature, tire pressure drops about 1 PSI, so tires that were properly inflated in summer may be low by winter.
Absolute pressure is measured from a perfect vacuum (zero). Gauge pressure is measured relative to ambient atmospheric pressure (~14.696 PSI / 101.3 kPa at sea level). When you pump your tires to 32 PSI, that's gauge pressure — the pressure above atmospheric. The actual absolute pressure inside the tire is about 46.7 PSI absolute. Most everyday pressure measurements (tires, blood pressure cuffs, pressure cookers) use gauge pressure. Scientific and industrial contexts often specify absolute. When in doubt, check whether "PSIg" (gauge) or "PSIa" (absolute) is indicated.
Blood pressure is measured in mmHg — millimeters of mercury. A reading of 120/80 means 120 mmHg systolic (when the heart beats) over 80 mmHg diastolic (between beats). In more familiar terms, 120 mmHg = 2.32 PSI = 16 kPa = 0.158 atm. Yes, your heart is pumping blood at a pressure of about 2.3 PSI — which sounds almost nothing until you realize it's sustained 60–100 times per minute for your entire life. Normal adult blood pressure is below 120/80; hypertension stage 1 starts at 130/80; hypertensive crisis is above 180/120 mmHg.
Atmospheric pressure decreases with altitude because there's less air above you pressing down. At sea level it's 1013.25 hPa (14.696 PSI). At 5,000 ft (1,524 m) it's about 843 hPa. At 10,000 ft (3,048 m) roughly 697 hPa. At 29,032 ft (Mount Everest summit) about 337 hPa — one-third of sea level. Practically: if you drive from sea level up to a mountain resort at 8,000 ft, sealed chip bags will puff up, your ears will pop, water boils at 92°C instead of 100°C, and tire pressure gauges will read slightly higher (because atmospheric reference pressure is lower). Altitude affects baking, cooking times, espresso extraction, and anything that depends on boiling point or leavening.
2.2 bar equals about 31.9 PSI — essentially 32 PSI. The conversion is 1 bar = 14.504 PSI, so multiply bar by 14.504 to get PSI. Common European tire specs and their PSI equivalents: 2.0 bar = 29 PSI, 2.2 bar = 32 PSI, 2.4 bar = 34.8 PSI, 2.5 bar = 36.3 PSI, 2.7 bar = 39.2 PSI. Many modern US tire gauges also show bar on the other side of the dial — just flip it over. If your gauge only shows PSI, round bar × 14.5 to get close enough for tires.