Straight length plus one total fitting length
Inputs: 100 ft straight length and 45 ft total source-based fitting length.
Calculation: Add the entered lengths.
Result: 145 ft TEL.
Pressure loss and static pressure
Duct Total Effective Length Calculator
Combine straight lengths and documented fitting allowances to total a duct route’s effective length.
Concepts behind this calculation
Add user-supplied fitting equivalent length to straight duct length for one defined airflow path, either as one total or an auditable fitting schedule.
Total effective length expresses a selected path as straight duct plus the equivalent straight length attributed to its fittings. It is a method-dependent pressure-accounting device, not the installed material length.
Fitting equivalent lengths must belong to the same sizing method and applicable geometry. A pressure coefficient cannot be pasted into a feet column without a compatible conversion.
How to use this calculator
- Choose straight length plus one total fitting length for a supplied allowance, or the fitting-schedule method for individual fitting quantities.
- Measure straight duct length along the selected route. For schedule mode document the equivalent-length table/method reference and enter fitting rows as equivalent length in feet and quantity.
- Check the straight and fitting subtotals for omissions and duplication before using TEL in a friction budget.
Calculation method and applicability
TEL = straight length + total fitting equivalent length; schedule TEL = straight length + Σ(equivalent lengthᵢ × quantityᵢ)
TEL and straight length are in feet. Each schedule equivalent length is ft per fitting; quantity is a count. Σ means sum the quantity-weighted equivalent lengths along the selected route.
Input definitions and units
- Length calculation
- Use one total when already reconciled, or schedule each fitting value and quantity from one compatible source basis. Choices: Straight length plus one total fitting length; Straight length plus fitting schedule.
- Straight duct length (ft)
- Total clear path length along the specified run.
- Total fitting equivalent length (ft)
- Enter values from one selected, compatible table/method and duct-size basis. Applies to Length calculation: Straight length plus one total fitting length.
- Equivalent-length table/method reference
- Identify the table, edition, fitting geometry, size and flow basis. This annotation is not authenticated. Applies to Length calculation: Straight length plus fitting schedule.
- Fitting equivalent length and quantity rows (equivalent length ft, quantity)
- Enter 1–100 rows. Each row is equivalent length in ft followed by a nonnegative quantity. The calculator sums only your supplied values; it does not provide a fitting table. Applies to Length calculation: Straight length plus fitting schedule.
How to interpret the result
Use TEL only with a compatible friction-budget method. The fitting subtotal is not extra installed duct and should not be reused as material takeoff length.
Worked examples
Straight length plus fitting schedule
Inputs: 100 ft straight length and rows 20 ft×2, 15 ft×1 and 5 ft×3.
Calculation: 100 + (20×2 + 15×1 + 5×3) = 170 ft.
Result: 170 ft TEL; supplied fitting equivalent-length total is 70 ft.
Assumptions and limits
- Equivalent-length values depend on fitting geometry, size, flow split and selected table/method.
- The schedule sums supplied values and quantities; it does not provide or verify the fitting table.
- Do not combine values based on incompatible standards, sizes or definitions.
FAQs
Should I include every branch in one TEL?
Use the complete route being assessed. Parallel routes are alternatives; adding their lengths together does not describe a single air path.
Does quantity include repeated fittings?
In schedule mode enter one fitting equivalent length and its count per row. Do not also include those same fittings in a separate lumped allowance.
Sources
- ACCA Manual D information pageThe full standard text and its fitting table values were not inspected; values must be sourced independently.
- ACCA: Calculating Friction Rate: It’s Not a ConstantMethod relationship context; not a table of fitting equivalent lengths.
Related calculators
Related reading
Available static pressure, TEL, and design friction rate Build a compatible pressure allowance for ducts and fittings, then divide it by a matching total effective length. Fitting K-factor vs. equivalent length Choose one fitting-loss representation that matches the geometry, flow path, velocity reference, and source data.