Free Voltage Drop Calculator Widget
The embedded Voltage Drop Calculator turns a wire size, current, one-way distance and source voltage into the voltage drop in volts and percent, the voltage at the load, and an ampacity check for the wire — for single-phase, DC or three-phase circuits. It fits electrician and electrical contractor sites, wire and cable suppliers, solar/battery system builders, and electrical how-to publishers.
It's a single iframe — free, responsive, no registration, and it adds no link, ad or tracking script to your page.
Live preview
The embed adds no link, no ads and no tracking to your page. Prefer a guided version with a preview? Use the embed builder.
One small ask
Nothing links back to us from the widget itself. If your readers find it useful, please add a credit link to the Voltage Drop Calculator somewhere on your page — that's what keeps it free to maintain and helps others discover it.
Where the Voltage Drop Calculator widget fits
- An electrician or electrical contractor's "services" or FAQ page
- A wire, cable or solar-equipment supplier's sizing or technical page
- A "how to calculate voltage drop" or wiring how-to article
How to add it to your site
- Plain HTML: drop the snippet in wherever the calculator should sit.
- WordPress: use a “Custom HTML” block for the snippet — the “Paragraph” block will strip the iframe out.
- Squarespace / Wix / Webflow: use their “Embed” / “Custom Code” / “HTML” element and drop the snippet in.
- The second line (
embed.js) is optional and just keeps the frame height fitted to the content — one copy per page covers every calculator on it.
Sizing & responsiveness
Use 100% width to fill whatever column it's in, or a fixed pixel value for a sidebar. Height takes care of itself with embed.js — the frame tracks the calculator's actual content, results included. Without that script the frame holds at 950px and still functions, just with a scrollbar on smaller screens.
Questions from site owners
Is there a cost or a catch?
No — it stays free with no account, no API key and no usage cap, and nothing is added to your page in exchange: no injected link, no ads, no tracking. If a tool ends up useful to your readers, a plain credit link somewhere on the page is appreciated, not required.
Does embedding it hurt page speed or collect visitor data?
It shouldn't — the calculator sits in an iframe, so it can't block your page from rendering, and it loads no third-party ad or analytics scripts and sets no cookies on your visitors. The optional auto-resize script is a few kilobytes and loads without blocking anything.
Does it check wire ampacity too, not just voltage drop?
Yes — it flags when the selected wire size's NEC ampacity is below the entered load current, independent of the voltage drop result, so a wire that passes on drop but fails on ampacity still gets caught.
Does it support three-phase circuits?
Yes — a circuit-type toggle switches between the single-phase/DC (×2) and three-phase (×√3) voltage drop formulas.
Can I resize it or set a fixed width?
Yes. Choose a responsive (100%) or a fixed-pixel width when you copy the code; the height auto-fits the calculator, with a fixed fallback if the resizer script is blocked.
Just need to run the numbers yourself? Use the full Voltage Drop Calculator — it has the formulas, a worked example and an FAQ. Or see all embeddable calculators.