Convert pascals (Pa) to inches of water gauge (in.wg), mm H₂O, mbar, kPa and psi, for duct, fan and filter pressures. Type in either box.
| Pa | in.wg | mm H₂O | mbar |
|---|---|---|---|
| 10 | 0.0401 | 1.02 | 0.1 |
| 12.5 | 0.0502 | 1.275 | 0.125 |
| 20 | 0.0803 | 2.039 | 0.2 |
| 25 | 0.1004 | 2.549 | 0.25 |
| 30 | 0.1204 | 3.059 | 0.3 |
| 40 | 0.1606 | 4.079 | 0.4 |
| 50 | 0.2007 | 5.099 | 0.5 |
| 60 | 0.2409 | 6.118 | 0.6 |
| 75 | 0.3011 | 7.648 | 0.75 |
| 100 | 0.4015 | 10.197 | 1 |
| 125 | 0.5018 | 12.746 | 1.25 |
| 150 | 0.6022 | 15.296 | 1.5 |
| 200 | 0.8029 | 20.394 | 2 |
| 250 | 1.004 | 25.493 | 2.5 |
| 300 | 1.204 | 30.591 | 3 |
| 375 | 1.505 | 38.239 | 3.75 |
| 400 | 1.606 | 40.789 | 4 |
| 500 | 2.007 | 50.986 | 5 |
| 600 | 2.409 | 61.183 | 6 |
| 750 | 3.011 | 76.479 | 7.5 |
| 1,000 | 4.015 | 101.97 | 10 |
| 1,250 | 5.018 | 127.46 | 12.5 |
| 1,500 | 6.022 | 152.96 | 15 |
| 2,000 | 8.029 | 203.94 | 20 |
| 2,500 | 10.037 | 254.93 | 25 |
| Application | Pa | in.wg |
|---|---|---|
| Duct friction rate (equal friction design) | 0.65 – 0.82 per m | 0.08 – 0.10 per 100 ft |
| Minimum stair pressurization difference, sprinklered (NFPA 92) | 12.4 | 0.05 |
| Fan coil unit external static pressure | 50 – 125 | 0.2 – 0.5 |
| Clean / dirty panel filter | 50 / 125 | 0.2 / 0.5 |
| AHU external static pressure | 250 – 625 | 1.0 – 2.5 |
Reference temperature: 1 in.wg is 249.09 Pa for water at 4 °C (39.2 °F) and 248.84 Pa at 60 °F. The difference is 0.1%, which does not matter in HVAC work.
Related: Fan Static Pressure Calculator, Stair Pressurization Calculator, Online Ductulator and ESP Calculation for AHU and FCU.
1 in.wg = 249.09 Pa (water at 4 °C), so 0.5 in.wg is 124.5 Pa and 2 in.wg is 498 Pa.
Divide by 249.09. For example, 500 Pa ÷ 249.09 = 2.01 in.wg.
Inches of water gauge (also in.wc or "WC) is the pressure that supports a column of water one inch high. It is the usual unit for duct, fan and filter pressures in US practice.
25.4 mm H₂O, since 1 inch is 25.4 mm. 1 mm H₂O = 9.807 Pa.
1 in.wg = 0.0361 psi; 27.7 in.wg = 1 psi.
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