NEC Box Fill Calc
NEC Box Fill in Seconds
Free · Designed for iPad. Not verified for macOS.
Box Fill Calc helps electricians verify NEC 314.16(B) compliance for every junction box — in seconds, right on the job site.
Count Each Wire:
- Add conductors by gauge (18 AWG through 6 AWG) with exact counts
- Grounding conductors, internal clamps, support fittings, and devices all count correctly per NEC rules
- Every conductor has its proper NEC Table 314.16(B) volume allowance
Know Instantly:
- Total fill in cubic inches with a clear pass/fail result
- Line-by-line breakdown so you can see exactly what's using your box volume
- How much room is left — or how much you're over
Switch Box Sizes Fast:
- 18 standard box sizes from NEC Table 314.16(A): round, square, device, and masonry
- Custom box volume for specialty enclosures
- See the marked volume for every standard box size
Why electricians choose Box Fill Calc:
- One-tap recalculate when you change a count or toggle a fitting
- Works offline — no cell service needed on the job site
- One-time purchase, no ads, no account, no subscription
- Clean, high-contrast interface for bright sunlight and dim mechanical rooms
Made for journeyman electricians, apprentices learning code, inspectors double-checking fill, and anyone who wires junction boxes and wants to pass inspection the first time.
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Updated App Store screenshots and product page visuals. App functionality is unchanged.
The developer, 光 杨, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
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Information
- Seller
- 光 杨
- Size
- 1 MB
- Category
- Utilities
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - iPad
Requires iPadOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Guang Yang