Convert Millimeters of Water to Kilopounds per Square Inch
Convert Millimeters of Water (mmH₂O) to Kilopounds per Square Inch (ksi) instantly and accurately.
Conversion Formula
ksi = mmH₂O × 1.422334331e-6
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 Kilopounds per Square Inch
One ksi (kilopound per square inch) = 1,000 psi ≈ 6.895 MPa - the standard engineering stress unit in the US. ASTM A36 structural steel: 36 ksi yield, 58-80 ksi tensile. ASTM A325 high-strength bolts: 92 ksi proof load. AISC steel construction tables, FAA/MIL-SPEC aerospace allowables, and ASME Section VIII pressure vessel design all use ksi. Fracture toughness (K_IC) for steels: 50-200 ksi·√in. Convenient because it keeps large structural stresses as manageable 3-digit numbers. 1 ksi = 6.895 MPa.
Quick Reference Table
| Millimeters of Water (mmH₂O) | Kilopounds per Square Inch (ksi) |
|---|---|
| 1 mmH₂O | 1.422 × 10-6 ksi |
| 2 mmH₂O | 2.845 × 10-6 ksi |
| 5 mmH₂O | 7.112 × 10-6 ksi |
| 10 mmH₂O | 1.422 × 10-5 ksi |
| 25 mmH₂O | 3.556 × 10-5 ksi |
| 50 mmH₂O | 7.112 × 10-5 ksi |
| 100 mmH₂O | 0.000142233 ksi |