Duct Fitting Loss Calculator
Elbows, tees, take-offs and dampers often lose more pressure than every foot of straight duct combined. Count the fittings, add the straight run, and get the total the fan has to overcome.
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Run Parameters
Airflow and section for this path.
Fittings on this run
Enter a quantity for each fitting present.
| Fitting | C | Qty |
|---|---|---|
| 90° elbow, smooth radius, r/D 1.5 | 0.15 | |
| 90° elbow, smooth radius, r/D 1.0 | 0.22 | |
| 90° elbow, 5-piece segmented | 0.24 | |
| 90° elbow, 3-piece segmented | 0.34 | |
| 45° elbow, smooth radius | 0.10 | |
| 90° mitred elbow, no vanes | 1.20 | |
| Tee or cross, flow into the branch | 1.00 | |
| Tee or cross, straight through | 0.10 | |
| 45° conical take-off | 0.50 | |
| Gradual reducer, 30° included | 0.05 | |
| Gradual expander, 20° included | 0.25 | |
| Sharp-edged duct entry | 0.50 | |
| Abrupt duct exit | 1.00 | |
| Volume control damper, fully open | 0.20 | |
| Fire damper, curtain type | 0.50 | |
| Flexible connector at the plant | 0.30 |
Total Pressure Drop
- Total loss on this path
- 0.055 in. w.g.
- Section velocity
- 1,132 FPM
Fittings plus straight duct
- Fitting losses (ΣC × VP)
- 0.000 in. w.g.
- Straight duct loss
- 0.055 in. w.g.
- Sum of loss coefficients ΣC
- 0.00
- Velocity pressure
- 0.080 in. w.g.
- Friction rate
- 0.0923 in. w.g./100 ft
- Equivalent diameter
- 18.0 in
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Important Disclaimer
This calculator is for preliminary design guidance only. Final duct sizing, construction, and installation must be performed by qualified professionals and comply with applicable codes and standards.