Voltage Drop Calculator
Calculate the volt drop for electrical circuits, calculation results with the volt drop percentage and the actual voltage drop in volts.
Calculate the voltage drop of electrical circuits
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How to calculate volt drop
To calculate the voltage drop, use the formula VD = (mV/A/m) x Ib x L ÷ 1000.
Where VD is the total Voltage Drop, mV/A/m is the milliVolt per Amp per meter voltage drop (loss) for a specific cable type and size combination, Ib is the design current in Amps, L is the length of the circuit/cable in meters.
- Enter the load value in Amps.
- Enter the supply voltage.
- Enter the cable length.
- Select a cable type.
- Select the phase (single phase / three phase).
- Calculate
Voltage drop calculation working example
- Load (Ib) = 32 Amps.
- Supply voltage (V) = 230V.
- Cable length (m) = 15 meters.
- Cable type = Flat twin and earth.
- Cable size = 6.0mm².
- mV/A/m = 7.3.
- Calculation VD = 7.3 (mV/A/m) x 32 (Amps) x 15 (meters) / 1000 = 3.5
- Result = 3.5 Volts.
A Flat Twin & Earth 6.0mm² volt drop (mV/A/m) = 7.3, so 7.3 x 32 Amps x 15 meters / 1000 = 3.5 volts.
Online Volt Drop Calculator
Give this free online voltage drop calculator a go, or download the app.
Volt Drop Regulations
525.1 – In the absence of any other consideration, under normal service conditions the voltage at the terminals of any fixed current-using equipment shall be greater than the lower limit corresponding to the product standard relevant to that equipment.
525.201 – Where fixed equipment current-using equipment is not subject of a product standard the voltage at the terminals shall be such as not to impair the safe functioning of that equipment.
525.202 – The above requirements are deemed to be satisfied if the voltage drop between the origin of the installation (usually the supply terminals) and a socket-outlet or the terminals of fixed current-using equipment does not exceed that stated in Appendix 4, section 6.4.
Source: BS 7671
Summary of Features
Electrical voltage drop calculator for electrical circuits.
Get the App
Download the Voltage Drop Calculator app to start calculating volt drop for your electrical circuits today.