What your readers can do with it
Voltage drop questions come from two directions: "is this cable big enough for this run?" and "how far can I run this cable?". The voltage drop calculator answers both, for single-phase AC, three-phase AC and DC, in metres or feet.
- Load as a current, or as kW with a power factor for motors.
- Copper or aluminium, sized in mm² or in AWG and kcmil.
- Limits for IEC 60364, BS 7671, AS/NZS 3000 and the NEC, filled in for the type of circuit, or the reader's own limit.
- Pass or fail, the voltage at the load, the power lost in the cable and the smallest size that meets the limit.
- A Maximum cable length tab, a list comparing every size, and options for conductor temperature, parallel sets and reactance.
Where it fits
A solar installer's blog can put it under a post about DC cable runs from the panels, where long low-voltage runs make the drop matter most. Training providers can embed it in a cable sizing module so learners check each exercise, and a US electrical blog can open it on the NEC with AWG sizes. Make clear, as the note at the bottom of the widget does, that it checks voltage drop only, not current-carrying capacity or protection.
Suggested size
The default frame is 1,200 px high and up to 960 px wide, which shows the inputs, the result and the summary cards. The numbered working below them takes the tool to about 1,860 px at that width and scrolls inside the frame. Set about 1,900 px if you want readers to see every step without scrolling, or keep the default to show the answer first. On a phone the tool is about 1,830 px tall.
Open it on a motor feeder
This link checks a 22 kW three-phase motor at 400 V and a power factor of 0.85, fed through 80 m of 10 mm² copper:
https://widemath.com/embed/voltage-drop-calculator/?sys=3ph&v=400&p=22&pf=0.85&len=80&size=10&mat=cu
The widget finds a drop of 10.68 V, or 2.67%, inside the 5% IEC 60364 limit for that circuit. Add &code=nec for US limits, &lu=ft for a length in feet, or &size=12awg for an AWG size.
Add it in three steps
- Load the example or set up your own on the full page and copy its link, then press Copy embed code.
- Paste it into the page's HTML, below your explanation of the formula.
- Repeat the safety note in your own text. The widget prints it at the bottom of the tool, below the working, where some readers will not scroll.
Frequently asked questions
Does the widget size cables for current as well?
No. It checks voltage drop only, not current-carrying capacity or protection, and a note at the bottom of the tool says so. Cables must still be sized to the local wiring code by a licensed electrician.
Can it use AWG and feet for US readers?
Yes. Readers switch the length to feet and the size to AWG or kcmil, and choose NEC as the code. A link can set all three with lu=ft, size=12awg and code=nec.
Can it work out the longest run for a cable?
Yes. The Maximum cable length tab takes the load, the cable size and the limit, and gives the longest one-way run that stays within it.
More calculator widgets
Want the explanations and worked examples as well? They are on the full Voltage Drop Calculator page. All 24 widgets, each with a Copy code button, are in the calculator widget gallery.
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19 engineering quantities, every unit at once, and a free-form box for compound units.