Your browser does not support JavaScript v1.1 (or you have this functionality turned off). Therefore, this calculator page will not function or display correctly.

Raceway Fill and Voltage-drop Calculator

Raceway and Mat'l
Bump size R-way Results
(trade in)
(trade in)
(trade in)
Coated Stl
Length (ft)
Cable ? Conductor groups Source Load V-drop Results
Quantity AWG Insul'n Type Mat'l (VL-L) 3Ø (A) pf (%) (%) (VL-L)

- Notes on usage -

  1. When the calculator icon appears next to the 'R-way Results' box, data has changed and you need to click on that icon to recalculate the sheet. After a recalc, as you change data, some of the 'Results' may be invalidated by the data change - those will be 'greyed out'. For example, changing the conductor count affects raceway size and estimated weight, but not the voltage drop.
  2. You can specify that the conductors are in a cable. You must supply the cable quantity, weight (if you want a weight calculation), and diameter ('O.D.'). Note that the weight is in pounds per thousand feet. For cables, the conductor quantities are ignored - the raceway fill is governed by the cable O.D.
  3. To change the number of rows in the table, use the dropdown field at the top of the 'Conductor groups' column.
  4. The 'Bump size' field increments the calculated raceway size by the quantity of trade sizes selected. This affects the calculated weights (only); sizes for nipples & seals are not changed from the calculated minimum.
  5. Note that the conductor size, insulation, and material combination you specify may not be readily available in the market, even though the calculator has manufacturer's data for it and produces 'Results' for same. You must verify availability.
  6. Raceway Size
    • !ERR! in a 'R-way Result' field indicates that - for the chosen raceway material - no raceway component of that type is large enough for the conductor configuration specified - or you supplied a cable O.D. of 0.
    • Rigid Plastic Conduit types A and EB have internal dimensions larger than Sched 40, so sizes calculated for Sched 40 will be adequate for these other types also.
    • Calculation methods are per NFPA-70 [1999, 2002, 2005, 2008, 2011, & 2014] requirements.
    • Conductor data are per NFPA-70 [2014] ch. 9 tables and selected manufacturer's data.
  7. Voltage-drop
    • For this calculation (only) the conductor length is increased by 5 ft. over the given raceway length as an allowance for termination tails.
    • Calculations are per ANSI/IEEE Std. 141 using data from Table 9 of the above-listed NFPA documents and EPRI resistivity factors for elements missing from that table. The voltage drop is calculated at a conductor temperature of 75C, with 60 Hz source and linear (non-VFD) loads.
  8. Raceway Weight
    • 'No data' in the 'Weight' field indicates the calculator lacks weight data for one of your selected components and therefore can't compute a total.
    • This calculation uses various manufacturer's data and should be a good approximation, but your mileage will vary based on the source of your materials and the particular product 'flavor' you choose. Multiple material and design configurations can sometimes fall into the same NEC raceway classification. In such cases, where I have data for multiple product flavors the calculator uses the heavier values. The approximated weight excludes couplings, fittings, hangers, etc. - only the raceway and conductor weights are summed.