Convert Feet of Water to Standard Atmospheres
Convert Feet of Water (ftH₂O) to Standard Atmospheres (atm) instantly and accurately.
Conversion Formula
atm = ftH₂O × 0.02949979689
About Feet of Water
One foot of water column (ftH₂O) ≈ 2,989 Pa - the US customary equivalent of cmH₂O used in civil and hydraulic engineering. Municipal water supply systems are designed for 40-80 psi head ≈ 92-184 ft; fire suppression sprinkler systems require minimum 7 psi ≈ 16 ft. Well pump specifications, sump pump head ratings, irrigation mainline pressure, and drainage calculations all use feet of head. 1 ft of water = 12 in WC = 0.4335 psi ≈ 2,989 Pa.
About Standard Atmospheres
The standard atmosphere (atm) = exactly 101,325 Pa - defined by the 10th CGPM (1954) as the reference air pressure at sea level. Used to define STP (0°C and 1 atm) for gas law and thermochemistry. Chemical equilibrium constants (Kp), Henry's law solubility, and thermodynamic tables are tabulated at 1 atm. ISA aviation standard: sea-level 1 atm / 15°C, pressure halving every ~5.5 km. Diving physics: +1 atm per 10 m depth (fresh water) so 30 m = 4 atm absolute. Diamond formation in Earth's mantle: ~50,000 atm. 1 atm = 101,325 Pa.
Quick Reference Table
| Feet of Water (ftH₂O) | Standard Atmospheres (atm) |
|---|---|
| 1 ftH₂O | 0.0294998 atm |
| 2 ftH₂O | 0.0589996 atm |
| 5 ftH₂O | 0.147499 atm |
| 10 ftH₂O | 0.294998 atm |
| 25 ftH₂O | 0.737495 atm |
| 50 ftH₂O | 1.47499 atm |
| 100 ftH₂O | 2.94998 atm |