Air Properties Table — Density, Viscosity & Thermal Values (0–300 °C)
Dry air at 1 atm from 0–300 °C: density, dynamic and kinematic viscosity, thermal conductivity, and Prandtl number per Cengel Table A-15 property data.
Updated August 18, 2026
Air is the working fluid of HVAC, the coolant of electronics, and the medium of every external-flow problem, and its properties move more than intuition suggests: heat a room’s air from 0 to 300 °C and density drops by half (buoyancy and fan laws), viscosity rises 70% (unlike liquids, gas viscosity grows with temperature), and kinematic viscosity — the one that sets Reynolds number — more than triples. Reading ν at the film temperature instead of assuming a cold-air value routinely shifts Re between laminar and turbulent regimes.
These are the dry-air values at one standard atmosphere from Cengel’s Table A-15, the property set most heat-transfer coursework and design checks assume. Density obeys the ideal gas law essentially exactly in this range — every ρ cell in this table is re-derived from ρ = P·M/(R·T) with M = 28.97 g/mol in our test suite and agrees within 0.05% — so for other pressures you can simply scale ρ (and ν, inversely) by the pressure ratio while keeping μ, k, and Pr unchanged.
One honest caveat baked into the sourcing: published air tables come in two slightly different families. Cengel’s conductivities (Touloukian data) sit about 2–3% below the Incropera/NIST family, which pushes Prandtl correspondingly higher (0.730 vs 0.707 at room temperature). Both are internally consistent; this chart stays within the Cengel family throughout rather than mixing datasets, and for humid air near saturation or altitudes far from sea level you should correct density before anything else.
Dry Air at 1 atm (101.325 kPa)
| T (°C) | ρ (kg/m³) | μ (µPa·s) | ν (mm²/s) | k (mW/m·K) | Pr |
|---|---|---|---|---|---|
| 0 | 1.292 | 17.29 | 13.38 | 23.64 | 0.7362 |
| 5 | 1.269 | 17.54 | 13.82 | 24.01 | 0.735 |
| 10 | 1.246 | 17.78 | 14.26 | 24.39 | 0.7336 |
| 15 | 1.225 | 18.02 | 14.70 | 24.76 | 0.7323 |
| 20 | 1.204 | 18.25 | 15.16 | 25.14 | 0.7309 |
| 25 | 1.184 | 18.49 | 15.62 | 25.51 | 0.7296 |
| 30 | 1.164 | 18.72 | 16.08 | 25.88 | 0.7282 |
| 40 | 1.127 | 19.18 | 17.02 | 26.62 | 0.7255 |
| 50 | 1.092 | 19.63 | 17.98 | 27.35 | 0.7228 |
| 60 | 1.059 | 20.08 | 18.96 | 28.08 | 0.7202 |
| 80 | 0.9994 | 20.96 | 20.97 | 29.53 | 0.7154 |
| 100 | 0.9458 | 21.81 | 23.06 | 30.95 | 0.7111 |
| 150 | 0.8338 | 23.80 | 28.51 | 35.00 | 0.699 |
| 200 | 0.7459 | 25.77 | 34.55 | 37.79 | 0.6974 |
| 300 | 0.6158 | 29.34 | 47.65 | 44.18 | 0.6935 |
Cengel & Ghajar Table A-15 values (EES dataset; Keenan gas tables + Touloukian transport properties). The 150 °C row is not published in Table A-15 (which jumps 140 → 160 °C) and is taken from Engineering ToolBox’s direct 150 °C entries — consistent with Incropera within 1.6% and with ideal-gas density within 0.05%. μ, k, and Pr are effectively pressure-independent near ambient; scale ρ proportionally (and ν inversely) with absolute pressure.
Sources & Further Reading
- Cengel & Ghajar, Heat and Mass Transfer (Table A-15) / Cengel & Cimbala, Fluid Mechanics, 3rd Ed. (Table A-9) — Properties of air at 1 atm; verified across two exact-matching reproductions
- Incropera / Bergman et al., Fundamentals of Heat and Mass Transfer, 7th Ed., Table A.4 — per-kelvin cross-check (dataset-family difference in k and Pr of ~2–3% noted)
- Engineering ToolBox — Air properties (density, viscosity, thermal conductivity, Prandtl number) for the 150 °C row and independent cross-checks
Frequently Asked Questions
Why does air’s viscosity increase with temperature when oil and water get thinner?
In liquids, viscosity comes from intermolecular cohesion, which heat breaks down. In gases it comes from molecules wandering between flow layers and trading momentum — hotter molecules move faster and trade more, so μ rises roughly with √T (Sutherland’s law). That is why hot exhaust is “thicker” to a fan than cold intake air, per this table about 70% more viscous at 300 °C than at 0 °C.
Which temperature do I look up for a convection calculation?
Use the film temperature — the average of the surface and the free-stream temperatures — for external flows and standard correlations; a 90 °C radiator in a 20 °C room reads properties at 55 °C, not at either extreme. For internal flows most correlations use the bulk mean temperature instead. Getting this wrong shifts ν, and therefore Reynolds number, by tens of percent.
How do I adjust these values for altitude or a pressurized duct?
Only density needs correcting in normal ranges: multiply ρ by (actual absolute pressure ÷ 101.325 kPa) at the same temperature, per the ideal gas law. Dynamic viscosity, conductivity, and Prandtl number are essentially pressure-independent, while kinematic viscosity ν = μ/ρ scales inversely with pressure. In Denver (≈83 kPa) air is about 18% less dense — which is exactly why fans move less mass flow there.
Is the Prandtl number here different from the 0.707 my textbook uses?
Slightly, and deliberately so. Incropera-family tables (NIST-consistent conductivity) give Pr ≈ 0.707 near room temperature, while Cengel’s Touloukian-based conductivity yields Pr ≈ 0.729–0.731. The ~3% gap is a documented dataset difference, not an error, and it is well inside the accuracy of any convection correlation you would plug it into. Just avoid mixing k from one family with Pr from the other.
Do these values hold for humid air?
Close but not exactly: water vapor is lighter than dry air (M = 18 vs 28.97 g/mol), so humid air is slightly LESS dense — about 1% lighter at 30 °C and 100% relative humidity. Viscosity and conductivity shift by similar small amounts. For comfort-range HVAC the dry-air table is standard practice; for drying, combustion, or cooling-tower work use psychrometric properties instead.
Try the Calculators
Air Properties Table — Density, Viscosity & Thermal Values (0–300 °C) — reuven.tools/reference/air-properties — verified against: Cengel & Ghajar, Heat and Mass Transfer (Table A-15) / Cengel & Cimbala, Fluid Mechanics, 3rd Ed. (Table A-9) — Properties of air at 1 atm; verified across two exact-matching reproductions; Incropera / Bergman et al., Fundamentals of Heat and Mass Transfer, 7th Ed., Table A.4 — per-kelvin cross-check (dataset-family difference in k and Pr of ~2–3% noted); Engineering ToolBox — Air properties (density, viscosity, thermal conductivity, Prandtl number) for the 150 °C row and independent cross-checks