Best Electrical Calculator Apps for iPhone 2026 — NEC Wire Sizing & Voltage Drop
The Best Electrical Calculator Apps for iPhone in 2026
The electrical trade has been through a major shift. ElectriCalc Pro moved to a $29.99/year subscription in 2025. Calculated Industries retired their standalone electrical tools. And new alternatives have emerged — some free, some paid, all cheaper than monthly subscriptions.
For electricians working with NEC 2023 or NEC 2026 codes, we’ve tested every current option. This guide covers what’s actually available, what each app does well, and which one makes sense for your daily workflow.
What Electricians Need to Calculate Daily
Most electrical work revolves around three calculations: voltage drop on runs longer than a few feet, wire sizing from NEC Tables 310.16 and 310.17, and Ohm’s law for troubleshooting.
Conduit fill, motor calculations, and service entrance sizing come up weekly or project-dependent. A good app nails the daily work first.
The Electrical Calculator Landscape in 2026
FieldLab Electrician NEC Calculator — $9.99 One-Time
FieldLab’s Electrician NEC Calculator launches native SwiftUI with both NEC 2023 and NEC 2026 tables bundled. No separate purchase for code updates.
What it covers:
- Voltage drop (single-phase and three-phase)
- Wire sizing with derating factors (ambient temperature, bundling, insulation type)
- Ohm’s law with power calculations
- Conduit fill by trade diameter and fill percentage
- NEC compliance alerts for oversized conductors
UI highlights: Dark mode by default, optimized for low-light panel work, full Dynamic Type support for older eyes, and offline operation.
Price: $9.99 one-time Code editions: NEC 2023 and NEC 2026 included Dark mode: Yes, by default Offline: Yes
Limitations: Motor calculations and service entrance sizing are on the roadmap but not yet in the app.
Our bias: We built this. We’re confident in the calculation accuracy, but we’re listing competitors fairly so you can decide.
ElectriCalc Pro — $29.99/Year
ElectriCalc Pro is Calculated Industries’ current electrical tool. It covers the full NEC calculation suite: wire sizing, voltage drop, conduit fill, Ohm’s law, motor calculations, and service entrance sizing.
The app has a 4.9-star rating with a loyal user base who’ve relied on it for years. The problem isn’t the tool — it’s the pricing model. ElectriCalc Pro moved to a subscription in 2025 after years as a one-time purchase.
Price: $29.99/year after 7-day free trial Code editions: Current edition (unclear if NEC 2026 will be included or cost extra) Dark mode: No Offline: Yes Annual cost: $29.99 minimum (likely higher with new editions)
Electrical Formulator — $19.99 One-Time
Electrical Formulator by Robert Huff is a one-time purchase covering voltage drop, wire sizing, Ohm’s law, and conduit fill. It’s a lean, focused tool without premium features.
The UI dates to around 2015. No dark mode, limited code edition support, and only 89 App Store reviews (4.7 stars). The app works but feels dated.
Price: $19.99 one-time Code editions: Limited to older NEC editions Dark mode: No Offline: Yes
NEC Code Calculator App — $14.99 One-Time
A specialized app focused on code lookups and calculations. Less feature-rich than ElectriCalc Pro but cheaper than Electrical Formulator.
Minimal user reviews (42 total, 4.6 stars), so usage data is thin. It’s a legitimate option if you’re looking for code compliance checking specifically.
Price: $14.99 one-time Code editions: NEC 2020 and NEC 2023 Dark mode: No Offline: Yes
Free Web Option: BuiltByFieldLab.com Calculators
BuiltByFieldLab.com offers free voltage drop, Ohm’s law, and wire size calculators in your browser. No account, no install, works on any device.
The free calculators handle standard scenarios: single-phase copper at 60°C, basic three-phase circuits, standard K-factors. They don’t cover every derating scenario or aluminum conductors, but for a quick field check on a typical residential run, they’re accurate and fast.
Try the free voltage drop calculator → Try the free Ohm’s law calculator → Try the free wire size calculator →
Price: Free Code editions: NEC 2023 and NEC 2026 Dark mode: No (browser-dependent) Offline: No
The Price Comparison Table
| App | Price | NEC 2023 | NEC 2026 | Dark Mode | Annual Cost |
|---|---|---|---|---|---|
| FieldLab Electrician NEC | $9.99 once | ✓ | ✓ | Yes | $0 |
| Electrical Formulator | $19.99 once | Older | No | No | $0 |
| NEC Code Calculator | $14.99 once | ✓ | ✓ | No | $0 |
| ElectriCalc Pro | $29.99/yr | ✓ | TBD | No | $29.99+ |
| BuiltByFieldLab.com (Web) | Free | ✓ | ✓ | No | $0 |
Detailed Feature Comparison
Voltage Drop Calculation
All paid apps handle voltage drop correctly using the standard formula: VD = (2 × K × I × D) / CM
Key difference: FieldLab’s app offers single-phase and three-phase with temperature derating built in. ElectriCalc Pro includes motor calculations (rotating equipment adds complexity). Electrical Formulator and NEC Code Calculator cover the basics but may not handle all derating scenarios.
Wire Sizing (NEC 310.16 & 310.17)
This is core to electrical work. Table 310.16 (60°C, 75°C, 90°C insulation) is the standard for most residential and light commercial. Table 310.17 is used occasionally for single-conductor cable.
FieldLab’s app includes both tables with automatic derating for:
- Ambient temperature (90°F to 140°F)
- Bundling adjustment factors (2-6 conductors grouped)
- Copper and aluminum conductors
ElectriCalc Pro covers all scenarios. Electrical Formulator and NEC Code Calculator are less clear on how comprehensively they handle derating — the app descriptions don’t specify.
Conduit Fill Compliance
Conduit fill calculations require NEC Chapter 9 Tables 1 and 4. Most electricians use the 40% rule (maximum fill for three or more conductors) as a practical shortcut.
All four paid apps handle this. The difference is UI clarity and how many conductor types they support.
Dark Mode Matters for Electrical Work
Electricians work in panels, basements, attics, and crawl spaces where the only light is a headlamp. A bright white calculator screen destroys your night vision and makes the headlamp less effective.
Only FieldLab’s app defaults to dark mode. ElectriCalc Pro, Electrical Formulator, and NEC Code Calculator all ship with light mode. You can set your phone to dark mode globally, but calculator apps don’t always respect that setting.
This is a small feature with disproportionate value for anyone doing dark-environment electrical work.
Which App to Choose
Choose FieldLab Electrician NEC ($9.99) If:
- You want the cheapest option with both NEC 2023 and 2026 included
- You work frequently in low-light environments (dark mode matters)
- You want offline access and don’t want monthly charges
- You calculate voltage drop and wire sizing regularly
- You prefer a modern, clean interface with Dark Type support
Choose ElectriCalc Pro ($29.99/year) If:
- You need motor calculations and service entrance sizing regularly
- You’ve used ElectriCalc Pro for years and want the full feature set
- You’re okay with subscription costs
- You need the most comprehensive NEC coverage
Reality check: You’ll pay $300 for ElectriCalc Pro over 10 years. FieldLab’s app costs $9.99 forever.
Choose Electrical Formulator ($19.99) If:
- You need a one-time purchase cheaper than ElectriCalc Pro
- You don’t calculate frequently enough to justify $29.99/year
- You can live with an older UI
Use Free Web Calculators If:
- You calculate electrically infrequently
- You have reliable WiFi/cellular at job sites
- You want to test before buying an app
- You work on Android (FieldLab apps are iOS-only)
NEC Code Edition Support in 2026
Important: Your state’s electrical code adoption schedule determines which NEC edition you actually need to use.
- NEC 2026: Adopted in CA, TX, FL, and some other states (varies by city/county)
- NEC 2023: Still the standard in many states
- NEC 2020: Still acceptable in some jurisdictions
Check your local adoption schedule before choosing an app. FieldLab’s app includes both NEC 2023 and 2026. ElectriCalc Pro’s stance on NEC 2026 isn’t yet clear (as of April 2026).
Check your state’s NEC adoption →
Frequently Asked Questions
Does FieldLab’s app calculate service entrance sizing?
Not yet. Voltage drop, wire sizing, Ohm’s law, and conduit fill are in the current version. Service entrance sizing (load calculation, main breaker sizing) is on the roadmap.
Which app is most accurate for voltage drop?
All four paid apps use the same formula (VD = 2KID/CM) specified in the NEC. If the K-factor, conductor size, and circuit length are identical, the results will match. FieldLab’s app uses standard K-values: 12.9 for copper, 21.2 for aluminum, both correct per NEC.
Can I sync results between my app and my office computer?
None of these apps currently offer cloud sync. Results stay on your device. You can manually export/screenshot calculations, but there’s no automatic backup.
Will ElectriCalc Pro charge extra for NEC 2026 updates?
Unknown as of April 2026. Historically, Calculated Industries charged extra for new NEC editions. Contact ElectriCalc Pro support if this is important for your decision.
Is dark mode worth paying more for?
In most trade work, yes. But it depends on your environment. If you work mostly in shops with good lighting, dark mode is nice-to-have. If you work in panels and basements regularly, it’s essential.
Can I use these apps on Android?
FieldLab’s calculator apps are iOS-only as of 2026. ElectriCalc Pro, Electrical Formulator, and NEC Code Calculator may have Android versions — check the Google Play Store. The free web calculators at BuiltByFieldLab.com work on any device with a browser.
Why is FieldLab’s app so cheap compared to competitors?
Lower overhead and different business model. We’re not beholden to private equity pressure to maximize recurring revenue. One-time purchase at $9.99 aligns with the trade — tools should work for you indefinitely, not require monthly fees.