CFM to kg/hr Air Mass Flow Calculator
Mass flow rate (kg/hr) is the actual quantity of air moving per unit time, independent of temperature and pressure. Volumetric flow (CFM) is the volume of air moving, which changes...
Formula
Source: Engineering Toolbox, ASHRAE | Last reviewed: June 12, 2026
Examples
1 CFM
= 2.038 CFM
1 CFM = 2.038 kg/hr of air at standard conditions
100 CFM
= 203.8 CFM
100 CFM compressor delivers ~204 kg/hr
500 CFM
= 1019 CFM
500 CFM = 1,019 kg/hr (~1 metric ton/hr of air)
Popular Conversions
Quick answers for the most-searched CFM to CFM values.
100 CFM to kg/hr
100 CFM = 203.8 CFM
Standard air at sea level, 68°F. 100 CFM = 203.8 kg/hr. This is a common compressed air flow for small workshops and laboratories.
500 CFM to kg/hr
500 CFM = 1019 CFM
Medium industrial compressed air flow. 500 CFM = 1,019 kg/hr (≈1 tonne/hr). Typical for mid-sized manufacturing plants with multiple pneumatic tools and actuators.
1000 CFM to kg/hr
1000 CFM = 2038 CFM
Large compressed air system. 1,000 CFM = 2,038 kg/hr. Found in automotive assembly, chemical processing, and large-scale manufacturing — typically requires multiple 200-300 HP compressors.
10 CFM to kg/hr
10 CFM = 20.38 CFM
Small compressor output. A 10 CFM compressor delivers about 20 kg/hr of air — sufficient for a single pneumatic tool or small laboratory air supply.
Where is this used?
HVAC outdoor air calculations: determining ventilation air mass for heating/cooling load computations.
Process air requirements: sizing air dryers and filters based on mass flow rather than volumetric flow.
In combustion engineering, the CFM-to-mass-flow conversion is the first step in any boiler, furnace, or process heater calculation — the stoichiometric air requirement is computed from the fuel composition and the mass flow of fuel, and the air is supplied in excess (typically 10–25% for natural gas burners, 20–50% for solid fuel boilers) to ensure complete combustion.
A 50 MMBtu/hr natural gas burner requires about 7,500 SCFM of air (about 15,300 kg/hr) at 10% excess, with the conversion applied at the burner manufacturer data sheet (typically in SCFH or SCFM) to the combustion calculation.
Compressed air energy audits per the DOE Compressed Air Challenge and CAGI Air Audit use mass flow directly — the specific energy consumption (kW per 100 SCFM or kg/hr of air delivered) is the primary efficiency metric, and modern efficient compressors at 100 psig deliver about 18 kW per 100 SCFM (or about 5.4 kW per 100 kg/hr of air).
HVAC heating and cooling load calculations for the ventilation (outdoor air) component use mass flow to handle the energy calculation at any altitude: the mass × cp × ΔT formula gives the sensible load, and mass × (W_outdoor − W_indoor) gives the latent load.
For a 10,000 CFM outdoor air system at sea level in 95°F / 90% RH summer conditions, the mass flow is 20,380 kg/hr of humid air (about 1.21 kg/m³ × 16,988 m³/hr), and the cooling load is 20,380 × 1.01 × (95 − 55) = 824,000 BTU/hr sensible plus a significant latent load.
Cleanroom and pharmaceutical isolator air flow calculations for ISO 14644 and EU GMP Annex 1 use mass flow for the particle dilution and the air change rate calculation, with the same density correction applying to cleanroom air at standard conditions (1.2 kg/m³ at 20°C and 1 atm).
Process gas mass flow metering in chemical plants, refineries, and air separation plants uses Coriolis meters (Endress+Hauser, Emerson, Yokogawa) that output mass flow directly in kg/hr, and the SCFM or Nm³/h equivalent is calculated from the mass flow and the gas density for reporting and custody transfer.
Industry Standards Referenced
Frequently Asked Questions
What density does this use for air?
Standard air density of 1.2 kg/m³ at 68°F (20°C) and sea level pressure. At other conditions, the mass flow changes. Hot air is less dense; high-altitude air is less dense. Use temperature and pressure corrections for precise work.
How does humidity affect the calculation?
Moist air is slightly less dense than dry air at the same temperature. At 90°F and 90% RH, the density drops to about 1.15 kg/m³, a ~4% reduction. For most industrial applications, dry air assumptions are adequate.
Can I use this for other gases?
No, this converter is specific to air. The factor 2.038 is derived from air density (1.2 kg/m³). For other gases, multiply by the ratio of the gas density to air density (approximately the molecular weight ratio).
How do I convert CFM to kg/hr at a different altitude?
The density correction factor is: ρ_actual = 1.2 × (P_actual / 14.7) × (528 / (T_actual + 460)). Then kg/hr = CFM × 0.0283168 × ρ_actual × 60. At 5,000 ft (12.2 psia), the factor drops to about 1.67 (instead of 2.038), meaning you get ~18% less mass flow for the same CFM.
Why use mass flow (kg/hr) instead of volumetric flow (CFM)?
Mass flow is independent of temperature and pressure — it tells you exactly how much substance is moving regardless of conditions. This matters for: combustion air calculations (stoichiometric ratios are mass-based), chemical process metering, compressed air energy audits (mass flow × specific power = kW), and custody transfer billing.
What is the difference between SCFM and kg/hr?
SCFM is a standardized volumetric flow at reference conditions. kg/hr is a true mass flow. The relationship: kg/hr = SCFM × 1.699 × 1.2 = SCFM × 2.038 at standard conditions. For non-standard conditions, you must first convert SCFM to ACFM, then convert ACFM to kg/hr using actual density.
Reviewed for accuracy
Reviewed against ASHRAE fundamentals and NIST property data for standard air density · Last reviewed: June 12, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.