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Free tool · Netlist
Netlist checker: one-pin nets, unnamed nets and duplicate designators
Paste a Protel, KiCad or OrCAD netlist and see the counts, the one-pin nets and the unnamed connections before they become layout questions.
The short answer
A netlist is the list of connections the layout has to make: every net names the pins it joins. The defects worth finding before routing are structural. A net with a single pin cannot be routed and is usually a schematic that lost a connection. An auto-named net means nobody named the signal. A reference designator used twice makes the bill of materials disagree with the assembly file. All three are text, so they can be found without a schematic or a CAD licence, and nothing needs to leave the browser.
Calculator
Netlist readiness checker
Paste the netlist text and the tool reads it in place: no upload, no account, no file. It recognises the three formats the practice actually receives — Protel/Altium, KiCad and OrCAD/Telesis — and reports the component, pin and net counts, the nets with a single pin, the auto-named nets and any duplicate designators. An unrecognised format is reported as unrecognised rather than guessed at.
What this tool readsThe netlist text, pasted in. Open the button for its units, why it matters and a typical value.
Nothing is uploaded
The parse runs in this page. No file and no netlist is sent anywhere, which is why the tool can accept a real customer netlist without a data-handling question.
What the netlist says
Counts first, then the findings that turn into questions during layout.
Paste a netlist to check it.
Paste a netlist, or load the sample
Protel/Altium, KiCad and OrCAD/Telesis formats are read. The sample shows every finding the checker reports.
Get an Instant QuoteEmail a layout engineer
Free, no account. The engineer reviews the inputs before a fixed quote is issued.
Want the derivation? Jump to the math behind the calculator.
The math
The formulas, with the working shown
Each equation is rendered with KaTeX, which also emits a MathML twin for screen readers and answer engines, explained in plain language, and copyable as LaTeX from the button in its corner. The variable list says what every symbol means; the model-limit note says where the formula stops being trustworthy.
Pins in a netlist
The pin total is what a quote and a placement file are built from, and the first number a netlist gives up.
- N
- number of nets
- \left| N_i \right|
- pins on net i
Every pin on every net is counted once. A component with eight pins contributes eight if all eight are connected.
The count checks against the schematic's own totals: if they disagree, a part is missing from the netlist rather than the board.
Model limits
Unconnected pins do not appear in a netlist at all, so a part with floating pins contributes fewer than its package's pin count.
One-pin nets
A net with one pin has nothing to connect to, so it cannot be routed and is almost always a mistake.
- n
- a net
- \left| \text{pins}(n) \right|
- number of pins on that net
The set is empty in a clean design. Every entry is a connection that ends nowhere, which in layout becomes a stub or a question.
The usual causes are a deleted wire, a test point that was never connected, or a pin renamed in the symbol and left orphaned.
Model limits
A deliberate single-pin net exists — a mounting hole tied to chassis, a test pad — but it should be named and documented, not discovered at handoff.
Average pins per net
A sanity number: a very low average means many nets are barely connected, and a very high one means a partial export.
- P
- total pins
- N
- number of nets
Digital boards usually average between three and six pins per net once power and ground are included. A value near two suggests a netlist of point-to-point links and probably a partial export.
It is not a defect test; it is the quickest way to notice the file is not the one you expected.
Model limits
Power and ground nets dominate the average when included, and are often absent from a PCB-only export. Compare like with like.
The connectivity requirement
A routable net joins two or more pins; anything less is not a connection.
- n
- every net in the design
This is the condition the one-pin set violates. It is stated separately because it is the rule the checker tests, and because a two-pin net is the minimum a router can act on.
The checker reports the count of violations rather than a pass or fail, because a deliberate test point is a legitimate exception the parser cannot know about.
Model limits
A net can satisfy this and still be wrong: two pins on the same component, or a net that shorts two supplies, both pass the count test and fail the design.
Defects
The three defects that cost the most later
A one-pin net is the classic: a wire was deleted in the schematic and the net kept one end. Layout cannot route it, so it either becomes a floating stub or a question halfway through the board. Finding it at handoff costs a minute; finding it after routing costs a re-spin of the affected area.
An auto-named net is the second: the tool named it because the designer never did, which usually means the connection was accidental. And a duplicate designator is the third: the same reference on two packages makes the BOM and the placement file disagree, which is a build-stopper rather than a layout one.
- A net with one pin cannot be routed and is usually a schematic slip.
- An auto-named net is a signal nobody named, and often a connection nobody meant.
- A duplicated designator breaks the BOM and the placement file silently.
- A format the tool does not recognise is reported, not guessed at.
Handoff
What a clean netlist saves
The netlist is the contract between the schematic and the layout. Every question about it after placement is a change order: a component moved, a net renamed, a pin swapped. Checking it before the first placement is the cheapest possible time to find a problem.
The same check is the first step of a netlist-to-Gerber engagement, which is why the tool reports counts as well as findings: the counts are what a quote is built from.
If the netlist is clean and the schematic is not, the netlist-to-Gerber layout service engagement starts from here; the DFM checks that follow it are on the DFM/DFA layout service page.
FAQ
Common questions
No. The parse runs in the page and the text never leaves the browser: there is no request, no storage key and no server-side copy. That is deliberate, because a checker is only useful if a real customer netlist can be pasted into it.
Want this checked on your board?
Send the stackup and interface list. We will check the netlist against the real layout before the quote is fixed.