Draw a single line diagram in your browser. No signup, no download, no watermark across your drawing, just a clean diagram. Add panels and equipment; the layout spaces everything automatically.
This is the same layout engine that powers the AmpSketch app. Feeders drop from the actual breaker position on the parent panel. Sibling equipment spaces itself so subtrees never collide. Rows line up across the drawing. When a run would cross unrelated wires, it becomes a pair of labeled tie stubs, the way a drafter would handle it. Panels widen as you add breakers and everything downstream re-spaces to match.
Generic diagram tools give you electrical symbols; you still do the drafting. Here the drafting is the software's job.
The free tool is for when you need a one line diagram by lunch. The app is for documenting a real building, whether you are mapping it from scratch in the field or taking an existing drawing to the site to verify it. Same engine, same drawing quality, different job.
| Free tool (this page) | AmpSketch app | |
|---|---|---|
| Draw with auto-layout | Yes | Yes |
| Data entry | You type it | Snap nameplate photos, AI reads kVA, voltage, trip ratings |
| Field verification | No | Walk the site with the drawing and confirm each piece is really there and rated as drawn |
| Export | PNG, browser print | PDF report: one-line, equipment schedule, floor plan, NEC flags |
| Floor plan | No | Panels pinned to locations |
| NEC checks | No | Flagged on the diagram as you go |
| Storage | This browser only | Cloud, multi-project, team workspace |
| Price | Free, no account | Free 14-day trial, then $69 per user per month |
Yes. Drawing, auto-layout, and PNG export are free with no account and no time limit. We make money on the AmpSketch app, which does field documentation on top of this same engine. The free tool is how you find out the engine is good.
No. Nothing on this page asks you to sign up. Your drawing autosaves locally in your browser.
The drawing autosaves to your browser's local storage on this device. Close the tab, come back tomorrow, it is still here. There is no cloud save in the free tool; that is part of the app.
A one line diagram (also called a single line diagram or SLD) is a simplified map of a power distribution system. Each three-phase circuit is drawn as a single line connecting equipment symbols: utility, transformers, switchgear, panels, breakers, loads. It is the drawing an electrician asks for first when they walk into an unfamiliar building.
Same drawing, two names. North America mostly says one line diagram; internationally it is usually single line diagram. Use whichever your reviewer uses.
Utility service, transformers, switchgear, panelboards with individual breaker slots and feed-thru lugs, generators, automatic transfer switches with normal and emergency feeds, motors, loads, and disconnects. Symbols follow standard one-line conventions.
When this drawing is a real facility. There are two ways people use the app. If you are mapping a system that has no drawings, you walk the site, snap each nameplate, and the one-line builds itself. If you already have a drawing (like the one you just made here, or an old as-built), you take it to the site and verify what is actually installed against it, piece by piece. Both end with a floor plan, NEC checks, an equipment schedule, and a PDF report. There is a free 14-day trial.
Is this drawing a real building?
AmpSketch is the app for that, two ways in. Map an existing system: walk the site, snap nameplates, the one-line builds itself. Or start from a drawing like this one, take it to the site, and verify what is actually installed against it. Either way you leave with the one-line, equipment schedule, floor plan, and PDF report.