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Electrical Panel Circuit Directory Slot Calculator

Calculate how many breaker slots are used and how many remain available in an electrical panel.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Available panel slots remaining

10 slots

High confidence
Slots used
30 slots

Running these inputs gives 10 as the available panel slots remaining. Slots used carries the most weight in this calculation, at 30 slots. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Add the equipment this sizes

This result is a specification — 10 slots — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Panel slot arithmetic: single-pole breakers occupy 1 slot each, double-pole (240V) breakers occupy 2 slots each; slots used = (single-pole count × 1) + (double-pole count × 2); slots available = total panel slots − slots used — standard panel schedule bookkeeping

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Frequently asked questions

How many slots does a double-pole breaker use?
A double-pole (240V) breaker occupies two panel slots, while a single-pole (120V) breaker occupies one — so slots used = (single-pole count × 1) + (double-pole count × 2).
What does a negative result mean?
A negative available-slots result means the panel is over capacity for the breakers listed. You would need to remove breakers or upgrade to a larger panel; a tandem/quad breaker only frees up slots where the panel and breaker manufacturer explicitly list them as compatible for that specific space.
Does this account for tandem or quad breakers?
No — this calculator counts standard single-pole and double-pole breakers only. Tandem and quad breakers are manufacturer- and panel-specific and should only be used where explicitly listed as compatible for that panel space.