A standard atmosphere is exactly 101,325 pascals.
Atmospheres to Hectopascals Converter — atm to hPa
Convert Atmosphere (atm) to Hectopascal (hPa) using the exact conversion factor (1 atmosphere = 1,013.25 hectopascal). See the formula, worked examples, conversion table, and common uses.
Atmospheres to Hectopascals converter
Converter
Pressure Converter
Convert pascals, bars, PSI, atmospheres, mercury columns, water columns, and engineering pressure units.
Context values
Some unit families need one extra value for a physically accurate result.
Hectopascal is 100 pascal units.
Result = input x 101325 / 100.
Pressure uses the pascal as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Atmospheres to Hectopascals
Atmosphere and Hectopascal both show up on pressure gauges — psi is standard on US tire and tool specifications, while bar is the everyday pressure unit across most of the rest of the world. Atmosphere is most often used for chemistry (standard conditions are often defined at 1 atm).
Formula
hectopascals = atmospheres × 1013.25
This factor comes from each unit's defined relationship to the category's base unit: 1 atmosphere equals 101325 base units, and 1 hectopascal equals 100 base units, so dividing one by the other gives the direct atmosphere-to-hectopascal factor of 1013.25.
Simple example
1 atm × 1013.25 = 1,013.25 hPa
1 atmosphere = 1,013.25 hectopascals.
Real-world example
35 atm × 1013.25 = 35,463.75 hPa
35 atmospheres = 35,463.75 hectopascals.
Conversion table
| Atmosphere (atm) | Hectopascal (hPa) |
|---|---|
| 1 atm | 1,013.25 hPa |
| 5 atm | 5,066.25 hPa |
| 10 atm | 10,132.5 hPa |
| 25 atm | 25,331.25 hPa |
| 50 atm | 50,662.5 hPa |
| 100 atm | 101,325 hPa |
Reverse conversion: Hectopascal to Atmosphere
1 hPa × 0.0009869232667 = 0.0009869233 atm
1 hectopascal = 0.0009869233 atmospheres.
atmospheres = hectopascals × 0.000986923266716
For a page dedicated to this direction, see Hectopascal to Atmosphere.
Understanding the Atmosphere
Atmosphere (atm) measures pressure. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. It is classified as a non-SI unit accepted for use with the SI.
Where it's used: Widely used internationally in chemistry, meteorology, and diving/aviation contexts alongside the pascal and bar
Uses of the Atmosphere today
- Chemistry (standard conditions are often defined at 1 atm)
- Diving and aviation pressure references
- General reference for everyday atmospheric pressure
Understanding the Hectopascal (hPa)
Hectopascal is 100 pascal units.
Atmosphere — sources
- BIPM SI Brochure — Standard atmosphere listed among non-SI units with a fixed exact value in pascals.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many hectopascals are in 1 atmosphere?
1 atmosphere equals 1,013.25 hectopascals, using the exact defined conversion factor rather than an estimate.
How do I convert atmosphere to hectopascal?
Multiply the atmosphere value by 1013.25. The converter above does this instantly to whatever precision you set.
How do I convert hectopascal back to atmosphere?
Use the reverse factor: 1 hectopascal equals 0.0009869233 atmospheres. You can also use the swap control in the converter above to flip the direction instantly.
What is a atmosphere?
Atmosphere (atm) measures pressure. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. It is classified as a non-SI unit accepted for use with the SI.
What is a hectopascal?
Hectopascal (hPa) is a unit of pressure.
Is the atmosphere to hectopascal conversion exact?
Yes. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Where is the atmosphere still used today?
Widely used internationally in chemistry, meteorology, and diving/aviation contexts alongside the pascal and bar