DC/ single phase calculation. The voltage drop V in volts (V) is equal to the wire current I in amps (A) times 2 times one way wire length L in feet (ft) times the wire resistance per 1000 feet R in ohms (Ω/kft) divided by 1000: Vdrop (V) = Iwire (A) × Rwire(Ω) = Iwire (A) × (2 × L(ft) × Rwire(Ω/kft) / 1000 (ft/kft)) The voltage drop V Forexample, let’s calculate the wire size of a 100-meter-long copper wire for a single-phase circuit when it must supply 30 amps of current with a 10 V voltage drop allowed: A (mm²) = 2 × 1.7241×10-8 Ω·m × 100 m × 30 A / 10 V × 1,000,000 A (mm²) = 10.3446×10-6 m² × 1,000,000 A (mm²) = 10.3446 mm². By comparing the size to the list of AWG wire sizes Thedownside of mixing 12/2 wiring on a 15 amp is that it confuses electricians, and someone could try to upgrade the breaker without realizing that there is also 14/2 wiring on the circuit. going from 14AWG to 12AWG confuses the use of the circuit by changing wire size -- future workers will see 12AWG and may make an assumption about the AWGto MM2 Explained. Since 1857, wire gauge to MM2 made determining a wire’s current-carrying ratings easier. AWG is determined by first figuring out the radius of a wire squared, time pi. Oftentimes the term “circular mil” is used. Circular mil is the area of a 1/1000 (or 1 mil) diameter circle. Such measurements are made on only the Ampacitybased on NEC ® Table 310.15(B)(16) (formerly Table 310.16) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, 60° through 90°C (140° through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F). AmpacityCalculator. Ampacity Charts. Wire Size & Amp Ratings. Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without 35. $39.95. 6+. $35.95. 15A twin core power cable for auto and marine applications PVC insulated white and red cable with black PVC outer jacket Sold per meter. Olex100m x 1mm White Electrical Building Cable Wire (0) $65. Add to Cart. Compare. Olex 1mm White Single Core Electrical Cable - Per Metre (0) $1.26. per metre. Narva 5m 255 Amp Battery And Starter Cable (0) $142. Add to Cart. Compare. Special Order. Narva 7m 140 Amp Battery And Starter Cable (0) $92.24. eAnBHu.