Convert Standard Atmospheres to Feet of Water
Convert Standard Atmospheres (atm) to Feet of Water (ftH₂O) instantly and accurately.
Conversion Formula
ftH₂O = atm × 33.89853848
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.
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.
Quick Reference Table
| Standard Atmospheres (atm) | Feet of Water (ftH₂O) |
|---|---|
| 1 atm | 33.8985 ftH₂O |
| 2 atm | 67.7971 ftH₂O |
| 5 atm | 169.493 ftH₂O |
| 10 atm | 338.985 ftH₂O |
| 25 atm | 847.463 ftH₂O |
| 50 atm | 1694.93 ftH₂O |
| 100 atm | 3389.85 ftH₂O |