# Kinematic Viscosity of Air Calculator

URL: https://speedycalculator.com/calculators/physics/kinematic-viscosity-of-air/
Last updated: 2026-10-30

> The kinematic viscosity of air calculator finds the density, dynamic viscosity (Sutherland's law) and kinematic viscosity of air at a given temperature and pressure.

## Inputs

- Temperature (°C, °F, K)
- Pressure (hPa, kPa, inHg, mmHg, psi, atm)
- Specific gas constant R_s (J/(kg·K))

## Results

- Density
- Dynamic viscosity
- Kinematic viscosity

## Formula

```
ρ = p/(R_s·T),  μ = μ₀·(T/T₀)^{3/2}·(T₀ + S)/(T + S)  (μ₀ = 1.716×10⁻⁵ Pa·s, T₀ = 273.15 K, S = 110.4 K),  ν = μ/ρ
```

## Explanation

Air's viscosity rises with temperature (unlike liquids), while its density falls, so kinematic viscosity rises quickly when air is heated. It is needed to compute Reynolds numbers for aircraft, cars and ventilation ducts.

### How to use the Kinematic Viscosity of Air Calculator

- **Temperature**
- **Pressure**
- **Specific gas constant R_s (J/(kg·K))**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the air temperature and pressure (and the specific gas constant if not standard air).

### Inputs explained

FieldWhat to enterTemperatureUnits: °C, °F, KPressureUnits: hPa, kPa, inHg, mmHg, psi, atmSpecific gas constant R_s (J/(kg·K))A number

### What each result means

- **Density** = [Pressure]÷([Specific gas constant R_s (J÷(kg·K))]×([Temperature] + 273.15))
- **Dynamic viscosity** = 1.716e-5×(([Temperature] + 273.15)÷273.15)^1.5×(273.15 + 110.4)÷([Temperature] + 273.15 + 110.4)×1e6
- **Kinematic viscosity** = [Dynamic viscosity]×1e-6÷[Density]

### Example values

How the main result changes when **Temperature** changes and everything else stays at the example values above:

Temperature (°C)Kinematic viscosity (mm²/s (cSt))1014.15861514.60642015.05932515.51743015.98064016.9221

## Worked example

Inputs — Temperature: 20 °C; Pressure: 1,013.25 hPa; Specific gas constant R_s (J/(kg·K)): 287.05.

Results — Density = 1.20412 kg/m³; Dynamic viscosity = 18.13322 µPa·s; **Kinematic viscosity = 15.05934 mm²/s (cSt)**.

## Key terms

- **Sutherland's law**: μ ∝ T^{3/2}/(T + S).

## FAQ

**What is the kinematic viscosity of air at 20 °C?**
About 15.1 mm²/s.

**Why does gas viscosity rise with temperature?**
Faster molecules transfer momentum more effectively.

**What is Sutherland's law?**
An empirical formula for gas viscosity versus temperature.

**Does pressure affect viscosity?**
Dynamic viscosity hardly; kinematic viscosity falls as pressure rises.


## Sources

- [U.S. Standard Atmosphere 1976 (NOAA/NASA/USAF)](https://ntrs.nasa.gov/citations/19770009539)
- [NOAA / National Weather Service – Weather calculators](https://www.weather.gov/epz/wxcalc)
- [NIST – Fundamental physical constants](https://physics.nist.gov/cuu/Constants/)