General Lighting & Receptacle Branch-Circuit Calculator

Size general lighting and receptacle branch circuits under NEC Articles 210 and 220 — with occupancy VA/ft² lookup, custom VA entry, continuous-load factor, receptacle and dedicated-load configuration, and a circuit designer with self-test mode.

AVAILABLEAUTOMATED CHECKS ONLYSTANDARDS-AWAREBEGINNERNECWHAT DO THESE STATUSES MEAN?

NEC • ART. 210 / 220VA/FT² TABLE LOOKUP5 OCCUPANCY PRESETS2017 / 2020 / 2026

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Overview

General lighting and receptacle branch circuits are among the first circuits sized on any commercial or residential project, and Articles 210 and 220 are among the most frequently referenced NEC sections in daily design practice. This calculator sizes branch circuits for general illumination and receptacle loads: enter floor area and select the occupancy type to pull the correct NEC Table 220.12 VA/ft² value (or enter a custom VA/ft²), configure general receptacle loads (15 A at 120 V, or special receptacle), and add dedicated loads. The continuous-load rule (125% on the circuit breaker and minimum conductor ampacity) is applied automatically, with an option to specify mixed continuous and non-continuous portions. The Loads tab provides a breakdown of connected load vs. calculated load vs. sizing load — three distinct values that are routinely confused. The Designer tab presents a branch-circuit layout tool showing how loads distribute across circuits. The Trace tab walks through the NEC Article 210 / 220 calculation sequence with code citations. A Self-Test tab runs the calculation logic against deterministic test cases. Five preset occupancy scenarios cover Small Office, Retail Space, Classroom, Receptacle-Heavy, and Dwelling Unit, with an Undersized scenario for learning what a violation looks like. The Learn tab covers the critical distinctions between connected load, calculated load, and sizing load; common branch-circuit mistakes; continuous vs. non-continuous load treatment; and NEC edition changes (2017, 2020, 2026). Supports NEC Articles 120, 210, and 220.

App preview

A live look at the app you'll launch — every control on the left drives the visualizations on the right in real time.

Inside the lab

Example data — not a real field report

Dashboard with occupancy VA/ft² and load summary — Dashboard — pick an occupancy preset (Small Office, Retail, Classroom, Dwelling, etc.) or enter a custom VA/ft²; connected, calculated, and sizing loads update live.

Load breakdown showing general lighting, receptacles, and dedicated loads — Loads — general lighting from Table 220.12, general 15 A / 120 V receptacles, and dedicated loads are itemized so you can see exactly what makes up the total.

Branch-circuit designer distributing loads across circuits — Designer — distributes loads across branch circuits and flags any that exceed the 80% continuous-load limit for a 15 A or 20 A breaker.

Calculation trace citing NEC 210 and 220 — Trace — walks through the Article 210 / 220 calculation sequence with code citations so every VA and every ampere is traceable.

NEC 210 and 220 references — References — Article 210 and 220 sections active for the current calculation, with edition-specific notes for 2017 / 2020 / 2026.

Learn tab covering connected vs calculated vs sizing load — Learn — the connected vs. calculated vs. sizing load distinction, common branch-circuit mistakes, and continuous vs. noncontinuous treatment.

What you'll do

01Look up the general lighting VA/ft² value from NEC Table 220.12 for a given occupancy type and calculate the total general lighting load for a defined floor area
02Distinguish connected load, calculated load, and sizing load and explain why all three values are different and matter
03Apply the 125% continuous-load multiplier to both the minimum conductor ampacity and the overcurrent device rating for a circuit serving continuous loads
04Configure a 15 A branch circuit for general receptacle loads and verify that the circuit loading does not exceed the 80% continuous-load limit
05Identify at least three common branch-circuit sizing mistakes the tool guards against and explain the NEC provision each mistake violates
06Compare how NEC 2017, 2020, and 2026 editions differ in their treatment of general lighting and receptacle branch-circuit requirements

Try a guided scenario

Build a branch circuit that includes both continuous and noncontinuous load.

Branch circuits and continuous loads · NEC Calculation Practice

No sign-in required. Progress is saved on this device.

What this lab is not

Not a design document, stamped calculation, or approval record.
Not a substitute for engineering analysis by a licensed professional.
Not a reproduction of NEC tables — values are computed and cited, and you must verify against the code edition enforced in your jurisdiction.
Not connected to live equipment and not a safety device.

Calculation basis

References NEC. Results are computed from the entered inputs and cited back to the referencing clause or table number — no code text or table is reproduced verbatim.

Simplifying assumptions are stated in the lab itself; where a model is intentionally conceptual, the lab says so rather than implying study-grade accuracy.

Standards basis: Standards-aware. Validation state: Automated checks only (last checked 2026-08-15).