Method and sources

NECwire performs arithmetic on published code tables. This page lists every table, the edition it was read from, the source it was verified against, and what could not be verified. NEC tables were checked on 2026-09-05; the German tables on 2026-09-05.

This site does not replace the NEC, the DIN VDE standards, the authority having jurisdiction, the equipment’s listing and instructions, or a licensed electrician. Local amendments apply and can be stricter than the tables here. “NEC” and “National Electrical Code” are marks of the NFPA; the site quotes the code and is not affiliated with the NFPA.

How verification worked

No NFPA copy is freely downloadable, so each table was read from an open reproduction of the NFPA-typeset text (course PDFs hosted by a construction-management program, a manufacturer’s technical PDF headed “NFPA 70: NEC-2023”, a state code that adopts the NEC, an IRC reprint) and then cross-checked cell by cell against a second, independent reproduction of another edition. A cell is marked verified only when both readings agree. Table 4 rows were also checked arithmetically (π/4 × ID² against the printed total, and each percentage column against the total). The engine tests in the repository pin spot cells so a transcription error fails the build.

NEC tables

What the code says about voltage drop

210.19(A) Informational Note No. 4: “Conductors for branch circuits as defined in Article 100, sized to prevent a voltage drop exceeding 3 percent at the farthest outlet of power, heating, and lighting loads, or combinations of such loads, and where the maximum total voltage drop on both feeders and branch circuits to the farthest outlet does not exceed 5 percent, provide reasonable efficiency of operation.” 215.2(A)(1) Informational Note No. 2 says the same for feeders. 90.5(C): “Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of informational notes. Such notes are informational only and are not enforceable as requirements of this Code.” Mandatory limits appear in 647.4(D) (sensitive electronic equipment; 2014 text) (“The voltage drop on any branch circuit shall not exceed 1.5 percent. The combined voltage drop of feeder and branch-circuit conductors shall not exceed 2.5 percent.”) and 695.7 (fire pumps; 2014 text). Quoted from the 2017 text; the 2023 wording could not be read from an open source.

The K-factor method is an approximation: it uses the DC resistance of Table 8 rounded to one constant per material and ignores reactance and the actual conductor temperature. The Table 9 method uses the published AC resistance and reactance for three conductors in conduit at 75 °C and 60 Hz; it is a better estimate for large conductors, low power factor and steel raceways. Neither replaces a measurement.

Termination rule

110.14(C)(1)(a): “Termination provisions of equipment for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG conductors, shall be used only for one of the following: (1) Conductors rated 60°C (140°F). (2) Conductors with higher temperature ratings, provided the ampacity of such conductors is determined based on the 60°C (140°F) ampacity of the conductor size used. (3) Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors.” (b): “Termination provisions of equipment for circuits rated over 100 amperes, or marked for conductors larger than 1 AWG, shall be used only for one of the following: (1) Conductors rated 75°C (167°F) (2) Conductors with higher temperature ratings, provided the ampacity of such conductors does not exceed the 75°C (167°F) ampacity of the conductor size used, or up to their ampacity if the equipment is listed and identified for use with such conductors” (2017 text).

Could not be verified: read these against your code book

• 2023 edition of Chapter 9 Tables 1, 4, 5, 8, 9 and of Tables 430.248/430.250/430.52. No open 2020 or 2023 copy was reachable. The 2005/2011/2014/2017 readings match cell for cell and no change is known, so the calculators cite 2017 with “identical to earlier editions” rather than claiming a 2023 reading.
• 240.4(D) aluminum limits (12 AWG 15 A, 10 AWG 25 A). Verbatim from 2017; the only 2023 confirmation is a manufacturer summary of unstated edition.
• Table 314.16(A), 4 × 1¼ round box, 8 AWG column. Prints 5 in NFPA 2011/2017 and 4 in IRC 2024. The calculator computes counts from volume and does not use the printed count.
• 110.14(C) 2023 structure. 2017 verbatim; the 2023 renumbering is confirmed only by a secondary summary. The rule is unchanged in substance.
• 647.4(D) and 695.7. Quoted from the 2014 text; later editions revised 695.7’s wording.
• Table 9 rows for 700, 800 and 900 kcmil and 14 AWG aluminum. Not in the table; the calculator says “not in Table 9” for those and shows only the K-factor result.
• Table 310.16 rows 14 AWG aluminum, 18/16 AWG at 60/75 °C. Printed as dashes; the calculator treats them as unavailable.
• DIN VDE 0298-4 Zuordnung In for 95 and 120 mm². Not printed in the source used; shown as “nicht tabelliert”.
• DIN 18015-1 and DIN VDE 0100-520 voltage-drop limits. Quoted from the trade press (elektro.net, 2020), not from the standards themselves.

German tables

DIN VDE 0298-4:2013-06: Strombelastbarkeit for Verlegearten A1, A2, B1, B2, C, E (Tabelle 3), temperature factors (Tabelle 17) and grouping factors (Tabelle 21), read from ABB STOTZ-KONTAKT, 2CDC 401 002 D0106 (11/13), Auszug mit Genehmigung des DIN/VDE and cross-checked against Westermann, Elektrische Installationen and the Swiss NIN worksheet 27.2. The In assignment table (1,5–70 mm²) is from Westermann. Voltage-drop limits (DIN 18015-1:2020-05 (Wohngebäude): 3 %; DIN VDE 0100-520 G.52.1: 3 % / 5 %; E DIN VDE 0100-520:2019-11: 4 %; VDE-AR-N 4100: 0,5 %) are quoted from elektro.net, de 21/2020. Conductivity κ = 56 (Cu) / 35 (Al) m/(Ω·mm²) at 20 °C from tgb-automation.de. Wallbox currents and cable recommendations from go-e, kabelkaufhaus.de, stromdiagnose.de and ADAC, dated on the Wallbox page. The German method page repeats this in German.

Cost pages

Each cost page lists the publishers fetched on the date shown, the range and average each prints, and the date the page states. The band is the lowest low to the highest high across those sources; where a publisher gives a national average it is shown as “typical” and averaged. No figure is invented; publishers that blocked access (Angi, Forbes Home, Thumbtack, The Spruce) are not cited even where a search snippet showed a number.

Privacy of what you type

The calculators run in the browser; the inputs live only in the page address so a result can be shared as a link. There is no server-side processing of what you enter. See the privacy policy.

Corrections

Send the table, row, the value you believe is right and the published source to hello@necwire.com. A wrong cell is one line in one file, and the tests will catch it next time.