Wire size & ampacity
Table 310.16 with ambient correction, bundling adjustment, 110.14(C) termination limits, the 240.4(D) small-conductor rule and a breaker recommendation.
For electricians, apprentices and inspectors
NEC calculators that show their work
Thirty-nine calculators and references: wire size, voltage drop, conduit and box fill, fault current, EV chargers, generators, solar PV, dwelling and multifamily loads, motors, transformers, conduit bending and the wiring rules inspectors check. Every answer in big type, with the NEC table cited and the math laid out so you can defend it.
Works offlineNo adsNo accountNEC 2017 · 2020 · 2023 · 2026
Every calculation an electrician runs, done right
Thirty-nine calculators and references built from the NEC tables, cross-checked, and unit-tested against textbook and handbook examples.
Voltage drop
DC, single-phase and three-phase, copper or aluminum, parallel sets, Table 8 resistance or Table 9 AC impedance with power factor. Find the drop, the minimum size, or the maximum run.
Conduit fill
EMT, IMC, RMC, PVC 40/80, FMC, LFMC, LFNC and ENT with Chapter 9 Tables 1, 4, 5 and 8. Mixed sizes, bare grounds, nipples. Fill %, smallest conduit, or most conductors that fit.
Box fill & pull boxes
314.16 volume counting for conductors, devices, clamps, fittings and grounding conductors with the smallest standard box that fits, plus 314.28 pull and junction box sizing for straight, angle and U pulls.
Motors, feeders & transformers
Full-load current from Tables 430.248 and 430.250, conductor sizing, Table 430.52 protection and overloads, multi-motor feeders per 430.24 and 430.62, and Table 450.3(B) transformer protection.
Dwelling, multifamily & service loads
Standard and optional Article 220 methods, added loads in existing dwellings (220.83), the multifamily optional method (220.84), the 310.12 dwelling service-conductor rule, and the resulting service size. Share the step list with the inspector.
Conduit bending
Offsets, rolling offsets, kicks, three- and four-point saddles, 90° stubs, back-to-back and segmented 90s, with numbered marks measured from the end of the pipe, shrink and bender take-up.
EV chargers, generators & solar
Does the charger fit the existing service? 220.87 metered demand, 220.57 EVSE load and the 625.42 energy-management setpoint. Standby generator sizing per 702.4 and 445.13. Solar PV conductors and fuses per 690.8 and 690.9, inverter output and the 705.12 busbar rule.
Fault current & parallel conductors
Point-to-point available fault current from transformer kVA and impedance or a known value, through each conductor run, for the 110.24 label. Parallel conductor sets per 310.10(G) with the equipment grounding conductor for each raceway.
Wiring rules
Receptacle spacing per 210.52 with suggested positions, a GFCI and AFCI checklist that follows your code edition, Table 300.5 burial depth, conduit and cable support spacing, and Annex I torque values.
Basics & conversions
Ohm's law, power and kVA, power-factor correction with capacitor kVAR, series and parallel resistance, conductor resistance at any temperature, and a unit converter with AWG to mm², hp to kW and torque.
References
Ampacity tables, AWG to mm² and resistance, standard breaker sizes, bend multipliers, NEMA plug and receptacle configurations, wire color codes for the US, Canada, IEC and UK.
Big answers you can read from arm's length
Designed for gloves, sunlight and dim electrical rooms.
Every calculator one tap away
Wire size with the NEC table cited
Voltage drop: %, minimum size or max run
Conduit fill in dark mode
Bending marks from the end of the pipe
Dwelling load and service size
Seven color themes
Large type built for the jobsite
Built for the jobsite, not the office
- Large type everywhereResults at 64 pt, inputs at 24 pt, touch targets sized for work gloves. Respects your phone's text size and stays readable in direct sun.
- Trade unitsType lengths the way you say them: 12-3/8 or 2' 6", with a fraction bar for sixteenths. Metric with one switch.
- Your code editionPick NEC 2017, 2020, 2023 or 2026. Edition-specific rules such as EV charger loads and box-fill counting follow your choice. All editions included, no add-ons.
- Show your workEvery result opens into the formula, the values used and the code section, and copies or shares as text.
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- Ohm's law
- Power & kVA
- Wire size & ampacity
- Voltage drop
- Conduit fill
- 310.12 service conductors
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- Everything in Free
- Box fill, pull boxes & grounding
- Motors, feeders & transformers
- Dwelling, multifamily & existing-dwelling loads
- EV charger, generator & solar PV sizing
- Fault current & parallel conductors
- Conduit bending, incl. rolling offsets and segmented 90s
- Wiring rules: receptacles, GFCI/AFCI, burial, support, torque
- PF correction, resistance, unit converter
- Quick tables, NEMA configs, wire colors
- Seven color themes
- Every NEC edition, now and future
Questions electricians ask
Which NEC editions does it support?
NEC 2017, 2020, 2023 and 2026. Choose the edition your jurisdiction has adopted in Settings; all calculators follow it. New editions are added as free updates.
Does it work without a signal?
Yes. Every table and formula is on the device. Nothing requires an account or a connection, including Pro after it is unlocked.
Is it a subscription?
No. The free tier is free forever. Pro is a single purchase of $12.99 that unlocks everything, on the App Store or Google Play, and restores on your other devices.
Can I trust the numbers?
Every table value was cross-checked against two published sources, and every calculator has unit tests against textbook examples. Each result cites the NEC section and shows the intermediate steps so you can verify it. The adopted code and the authority having jurisdiction always govern the installation.
Can it tell me whether an EV charger fits the existing service?
Yes. Enter the service rating and either the metered peak demand (220.87) or the calculated load, then the chargers. It reports the total against the service, and if it does not fit, the energy-management setpoint (625.42) that would make it fit.
Does it calculate available fault current?
Yes. The point-to-point method used by the industry: transformer kVA and impedance or a known value at the start, then each conductor run by size, material and length, giving the value for the 110.24 label.
Does it cover generators and solar?
Standby generator sizing from metered or calculated load with the 702.4 transfer rules and 445.13 conductors, and solar PV source-circuit conductors and fuses per 690.8 and 690.9, plus the 705.12 busbar rule for the inverter breaker.
Does it do metric?
Yes. Switch units in Settings: lengths in millimetres, AWG to mm² conversions, and the same calculators.
Does it run on tablets?
Yes. iPad and Android tablets get a wider layout with the same large type.