Convert Pounds per Square Foot to Millimeters of Water
Convert Pounds per Square Foot (lbf/ft²) to Millimeters of Water (mmH₂O) instantly and accurately.
Conversion Formula
mmH₂O = lbf/ft² × 4.882427636
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.
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.
Quick Reference Table
| Pounds per Square Foot (lbf/ft²) | Millimeters of Water (mmH₂O) |
|---|---|
| 1 lbf/ft² | 4.88243 mmH₂O |
| 2 lbf/ft² | 9.76486 mmH₂O |
| 5 lbf/ft² | 24.4121 mmH₂O |
| 10 lbf/ft² | 48.8243 mmH₂O |
| 25 lbf/ft² | 122.061 mmH₂O |
| 50 lbf/ft² | 244.121 mmH₂O |
| 100 lbf/ft² | 488.243 mmH₂O |