MEP Unit Converter: engineer's guide
MEP work crosses metric and imperial constantly. This converter handles the common HVAC, plumbing, and electrical conversions in one place.
What this calculator does
The tool converts between the most common HVAC (cooling, airflow), plumbing (water flow, pressure, head), and electrical (power, current) units.
Formulas used
- Common conversions:
1 kW = 3412 BTU/h = 0.284 TR; 1 CFM = 0.472 L/s; 1 GPM = 0.063 L/s; 1 psi = 6.895 kPa = 0.0689 bar; 1 ft = 0.3048 m
Variables
- kW/BTU/TR for cooling
- CFM/L/s/m³/h for airflow
- GPM/LPS for water flow
- psi/bar/kPa/mH2O for pressure
Worked example
Scenario: Chiller schedule from a US project used on a GCC job.
- 400 TR → 400 × 3.517 = 1407 kW cooling
- 3000 GPM → 3000 × 0.063 = 189 L/s
- 150 ft head → 150 × 0.3048 = 45.7 m
- 20 psi discharge → 20 × 6.895 = 138 kPa
Common mistakes to avoid
- Confusing TR (cooling) with tonne (mass)
- Using ft head vs psi without conversion (1 psi ≈ 2.31 ft)
- CFM vs SCFM (standard conditions vs actual)
Frequently asked questions
SCFM vs ACFM?
SCFM at standard conditions (14.7 psia, 68°F); ACFM at actual conditions. Differ at altitude and high temperature.
psi(g) vs psi(a)?
gauge vs absolute; differ by 14.7 psi. Pumps and pipes usually use gauge.
Standards and references
ISO 80000, ASHRAE unit conversion tables
Related tools on this site
Open the calculator that pairs with this guide: MEP Unit Converter.
Verification note
This guide is planning support only. Final design must be verified against the applicable project specification, authority requirements, manufacturer data, and the standards cited above. Consult a licensed engineer for construction-issue calculations.