Convert Millimeters of Water to Pounds per Square Foot
Convert Millimeters of Water (mmH₂O) to Pounds per Square Foot (lbf/ft²) instantly and accurately.
Conversion Formula
lbf/ft² = mmH₂O × 0.2048161436
About Millimeters of Water
One millimetre of water column (mmH₂O) = pressure from 1 mm of fresh water at standard gravity = exactly 9.80665 Pa. Preferred for very low differential pressures in HVAC: ductwork static pressures, fan curves, filter resistance, and building pressurisation are in mm WC. Gas valve operating pressures are typically 0.5-3 mm WC; clean-room cascade differentials 12-25 mm WC. A domestic gas hob manifold operates at ~20 mm WC on natural gas. Also used in spirometer calibration and hospital oxygen delivery systems. 1 mmH₂O = 9.80665 Pa.
About Pounds per Square Foot
One pound per square foot (psf) ≈ 47.88 Pa - the standard structural engineering load unit in US practice. Building codes specify design loads in psf: residential floors 40 psf; office buildings 50-80 psf; assembly areas 100+ psf; snow loads can exceed 100 psf. Wind pressure on building facades, soil bearing capacity for shallow foundations, and lateral earth pressure in retaining walls are all in psf. The related unit ksf (1,000 psf = 47.88 kPa) covers higher-capacity soils and deep foundations. 1 psf = 47.88 Pa.
Quick Reference Table
| Millimeters of Water (mmH₂O) | Pounds per Square Foot (lbf/ft²) |
|---|---|
| 1 mmH₂O | 0.204816 lbf/ft² |
| 2 mmH₂O | 0.409632 lbf/ft² |
| 5 mmH₂O | 1.02408 lbf/ft² |
| 10 mmH₂O | 2.04816 lbf/ft² |
| 25 mmH₂O | 5.1204 lbf/ft² |
| 50 mmH₂O | 10.2408 lbf/ft² |
| 100 mmH₂O | 20.4816 lbf/ft² |