µg/m³ to PPB (Air) Converter
Common Conversions
| µg/m³ | ppb (air) |
|---|---|
| 0.1 | 2.445/MW |
| 1 | 24.45/MW |
| 5 | 122.25/MW |
| 10 | 244.5/MW |
| 25 | 611.25/MW |
| 50 | 1222.5/MW |
| 100 | 2445/MW |
| 250 | 6112.5/MW |
| 500 | 12225/MW |
| 1000 | 24450/MW |
| 5000 | 122250/MW |
| 10000 | 244500/MW |
Why this conversion matters in chemistry
Ambient air-quality monitoring is a place this matters. A 125 µg/m³ ozone hourly average from a federal reference method monitor (MW 48 for O₃) converts to about 64 ppb at 25 °C — close to the EPA NAAQS 8-hour primary standard of 70 ppb that the AQI communication framework uses against state implementation plan compliance reporting. The conversion uses the ideal-gas molar volume (24.45 L/mol at 25 °C, 1 atm). What this is, really: the step between µg/m³ instrument output and the ppb form Clean Air Act standards default to.
Formula
ppb = (µg/m³ × 24.45) ÷ MW
Worked Examples
1 µg/m³ CO (MW 28) = 0.873 ppb
About a trace CO ambient reading.
10 µg/m³ NO₂ (MW 46) = 5.31 ppb
About a typical urban ambient NO₂ level.
100 µg/m³ O₃ (MW 48) = 50.94 ppb
About a moderate ambient ozone reading.
40 µg/m³ HCHO (MW 30) = 32.60 ppb
About a typical indoor formaldehyde level.
Frequently Asked Questions
How do I convert µg/m³ to ppb in air?
Multiply by 24.45 and divide by the molecular weight: ppb = (µg/m³ × 24.45) ÷ MW. Same form as the mg/m³-to-ppm conversion, just scaled by 1000.
What temperature does the formula assume?
25 °C (298.15 K) at 1 atm — the conditions for which 24.45 L/mol is the ideal-gas molar volume. At other conditions, recompute the molar volume from PV = nRT.
What are typical ambient air levels?
Urban NO₂: 10–80 µg/m³. Ozone: 20–200 µg/m³. CO: 500–10,000 µg/m³. PM₂.₅: 5–50 µg/m³ (particles, not gas-phase, so the conversion does not apply to PM).