What is on this sheet?

Conductor sizes with mm², circular mils and THHN area plus base ampacity; how many 12 AWG THHN conductors fit each trade size; the ambient temperature and conductor-count correction factors; voltage drop on 120 V circuits; and the IEC tabulated capacities for metric cable, with the PVC and XLPE columns side by side. Every table prints the clause it comes from.

Do the ampacity columns include the correction factors?

No. They are base table values: 30°C ambient, three or fewer current-carrying conductors and no termination limit. Apply the ambient factor and the conductor-count factor printed on the same sheet, then cap the result at the termination value for the equipment you have.

Can I use the IEC table for a North American job, or the NEC table in Europe?

No. The two sets are not interchangeable. They rest on different installation methods, reference conditions and grouping rules, so a number lifted from one cannot stand in for the other. Use the table that belongs to the standard your installation is inspected against — both are printed here so nothing has to be converted by hand.

Is the metric table just the AWG column converted?

No. A mm² to AWG conversion is geometry only: it compares cross-sectional areas. The IEC capacities depend on insulation, installation method, ambient temperature and grouping, which is why they are printed as their own table. For the conversion itself, use the mm² to AWG chart.

Can I print it, or hand it to someone else?

Yes. The sheet is free, needs no signup and prints on landscape A4 or Letter; the PDF is generated in the browser, so nothing is uploaded. If you pass it on, a link back to this page is appreciated and keeps the version current.

How are the values produced?

Every cell is computed by this site's calculation engine from registered constants rather than typed by hand, so the page, the PDF and the calculators cannot drift apart. The methodology page lists each source, its clause and its review status.

Reference

Electrical Quick Reference

One page of the numbers that come up constantly on the job: conductor areas, base ampacity, conduit fill counts, correction factors and voltage drop — in AWG/kcmil and in mm². The NEC tables and the IEC tables are kept separate on purpose: the two systems assume different installation conditions and are not interchangeable. Every figure is computed live by the same engine as the calculators, and every table names the clause it comes from.

Conductor sizes, areas and base ampacity

Ampacity columns are base table values: 30°C ambient, three or fewer current-carrying conductors, before any termination limit. Apply the corrections below before using them.

Size	mm²	Circular mils	THHN area (sq in)	Cu 60°C	Cu 75°C	Cu 90°C	Al 75°C
14	2.08	4,110	0.0097	15 A	20 A	25 A	—
12	3.31	6,530	0.0133	20 A	25 A	30 A	20 A
10	5.26	10,380	0.0211	30 A	35 A	40 A	30 A
8	8.37	16,510	0.0366	40 A	50 A	55 A	40 A
6	13.3	26,240	0.0507	55 A	65 A	75 A	50 A
4	21.15	41,740	0.0824	70 A	85 A	95 A	65 A
3	26.66	52,620	0.0973	85 A	100 A	115 A	75 A
2	33.63	66,360	0.1158	95 A	115 A	130 A	90 A
1	42.41	83,690	0.1562	110 A	130 A	145 A	100 A
1/0	53.51	105,600	0.1855	125 A	150 A	170 A	120 A
2/0	67.44	133,100	0.2223	145 A	175 A	195 A	135 A
3/0	85.03	167,800	0.2679	165 A	200 A	225 A	155 A
4/0	107.22	211,600	0.3237	195 A	230 A	260 A	180 A
250	126.68	250,000	0.397	215 A	255 A	290 A	205 A
300	152.01	300,000	0.4608	240 A	285 A	320 A	230 A
350	177.35	350,000	0.5242	260 A	310 A	350 A	250 A
400	202.68	400,000	0.5863	280 A	335 A	380 A	270 A
500	253.35	500,000	0.7073	320 A	380 A	430 A	310 A
600	304.02	600,000	0.8676	350 A	420 A	475 A	340 A
750	380.03	750,000	1.0496	400 A	475 A	535 A	385 A
1000	506.71	1,000,000	1.3478	455 A	545 A	615 A	445 A

Reference: NEC 310.16 (ampacity); NEC Chapter 9, Table 5 (THHN area); geometry (mm²)

Conduit fill: how many 12 AWG THHN conductors fit

Each count is the largest number of identical THHN/THWN-2 conductors that Chapter 9, Table 1 and Note 7 permit: 53% for one, 31% for two, and 40% for three or more. A decimal fraction of 0.8 or larger rounds up. The equipment grounding conductor is not included. A thicker insulation takes more space.

Trade size	EMT	PVC40	RMC	IMC
1/2 in	9	8	9	10
3/4 in	16	15	16	17
1 in	26	25	26	29
1-1/4 in	45	43	46	49
1-1/2 in	61	59	62	67
2 in	101	99	102	109
2-1/2 in	176	141	146	154
3 in	266	218	225	238
3-1/2 in	347	293	301	318
4 in	443	377	387	410

Reference: NEC Chapter 9, Table 1 (fill limits) and Table 4 (conduit internal area)

Ambient temperature correction factors

Multiply the base ampacity by the factor in the row for the ambient temperature the raceway actually runs through.

Ambient	60°C conductor	75°C conductor	90°C conductor
10 or less	x 1.29	x 1.2	x 1.15
11–15	x 1.22	x 1.15	x 1.12
16–20	x 1.15	x 1.11	x 1.08
21–25	x 1.08	x 1.05	x 1.04
26–30	x 1	x 1	x 1
31–35	x 0.91	x 0.94	x 0.96
36–40	x 0.82	x 0.88	x 0.91
41–45	x 0.71	x 0.82	x 0.87
46–50	x 0.58	x 0.75	x 0.82
51–55	x 0.41	x 0.67	x 0.76
56–60	—	x 0.58	x 0.71
61–65	—	x 0.47	x 0.65
66–70	—	x 0.33	x 0.58
71–75	—	—	x 0.5
76–80	—	—	x 0.41
81–85	—	—	x 0.29

Reference: NEC Table 310.15(B)(1)(1)

Conductor-count adjustment factors

Applies once more than three current-carrying conductors share a raceway. The equipment grounding conductor does not count here, but it does count for conduit fill.

Current-carrying conductors	Factor
4–6	x 0.8
7–9	x 0.7
10–20	x 0.5
21–30	x 0.45
31–40	x 0.4
41 or more	x 0.35

Reference: NEC 310.15(C)(1)

Voltage drop at 120 V, 15 A, single phase

Copper conductors, one-way lengths, computed with the resistance constant K. The feeder and branch-circuit recommendation is 3% or less; the combined path is 5%.

Size	50 ft	100 ft	150 ft
14 AWG (2.08 mm²)	3.92 %	7.85 %	11.77 %
12 AWG (3.31 mm²)	2.47 %	4.94 %	7.41 %
10 AWG (5.26 mm²)	1.55 %	3.11 %	4.66 %
8 AWG (8.37 mm²)	0.98 %	1.95 %	2.93 %
6 AWG (13.3 mm²)	0.61 %	1.23 %	1.84 %

Reference: K derived from NEC Chapter 9, Table 8; 3% recommendation from NEC 210.19(A)(1) Informational Note

Copper cable capacity by nominal size (IEC)

Tabulated capacities at the reference conditions: reference method C, air at 30°C, single circuit, no grouping. Method C is cable clipped direct. Within the air methods on this page (A1 to C) it is the highest; the buried methods D1 and D2 use a 20°C soil reference and can exceed C at small sizes, and the free-air E, F and G methods are higher still but are not included here. Values are taken from IEC 60364-5-52:2009. The 2024 consolidated edition has not been checked for changes to these tables — verify against the edition in force where the installation will be inspected.

Size	PVC, 2 loaded	PVC, 3 loaded	XLPE, 2 loaded	XLPE, 3 loaded
1.5 mm²	19.5 A	17.5 A	24 A	22 A
2.5 mm²	27 A	24 A	33 A	30 A
4 mm²	36 A	32 A	45 A	40 A
6 mm²	46 A	41 A	58 A	52 A
10 mm²	63 A	57 A	80 A	71 A
16 mm²	85 A	76 A	107 A	96 A
25 mm²	112 A	96 A	138 A	119 A
35 mm²	138 A	119 A	171 A	147 A
50 mm²	168 A	144 A	209 A	179 A
70 mm²	213 A	184 A	269 A	229 A
95 mm²	258 A	223 A	328 A	278 A
120 mm²	299 A	259 A	382 A	322 A
150 mm²	344 A	299 A	441 A	371 A
185 mm²	392 A	341 A	506 A	424 A
240 mm²	461 A	403 A	599 A	500 A
300 mm²	530 A	464 A	693 A	576 A

Reference: IEC 60364-5-52:2009, Tables B.52.2 / B.52.3 (2 loaded conductors) and B.52.4 / B.52.5 (3 loaded conductors)

Aluminum cable capacity by nominal size (IEC)

Size	PVC, 2 loaded	PVC, 3 loaded	XLPE, 2 loaded	XLPE, 3 loaded
16 mm²	66 A	59 A	84 A	76 A
25 mm²	83 A	73 A	101 A	90 A
35 mm²	103 A	90 A	126 A	112 A
50 mm²	125 A	110 A	154 A	136 A
70 mm²	160 A	140 A	198 A	174 A
95 mm²	195 A	170 A	241 A	211 A
120 mm²	226 A	197 A	280 A	245 A
150 mm²	261 A	227 A	324 A	283 A
185 mm²	298 A	259 A	371 A	323 A
240 mm²	352 A	305 A	439 A	382 A
300 mm²	406 A	351 A	508 A	440 A

Reference: IEC 60364-5-52:2009, Tables B.52.2 / B.52.3 (2 loaded conductors) and B.52.4 / B.52.5 (3 loaded conductors)

Ambient temperature correction, air (IEC)

Multiply the tabulated capacity by the factor for the ambient the cable actually runs through. Above the tabulated range the standard gives no value.

Ambient	PVC (70°C)	XLPE (90°C)
up to 10°C	x 1.22	x 1.15
up to 15°C	x 1.17	x 1.12
up to 20°C	x 1.12	x 1.08
up to 25°C	x 1.06	x 1.04
up to 30°C	x 1	x 1
up to 35°C	x 0.94	x 0.96
up to 40°C	x 0.87	x 0.91
up to 45°C	x 0.79	x 0.87
up to 50°C	x 0.71	x 0.82
up to 55°C	x 0.61	x 0.76
up to 60°C	x 0.5	x 0.71
up to 65°C	—	x 0.65
up to 70°C	—	x 0.58
up to 75°C	—	x 0.5
up to 80°C	—	x 0.41

Reference: IEC 60364-5-52:2009, Table B.52.14 (air, 30°C reference)

Educational and design-planning reference only — not professional engineering advice. NEC table values reflect NEC 2023 and are pending review; the 2026 edition has not been verified. Installation must be carried out by a licensed electrician in accordance with the code enforced locally.

Frequently asked

What is on this sheet?: Conductor sizes with mm², circular mils and THHN area plus base ampacity; how many 12 AWG THHN conductors fit each trade size; the ambient temperature and conductor-count correction factors; voltage drop on 120 V circuits; and the IEC tabulated capacities for metric cable, with the PVC and XLPE columns side by side. Every table prints the clause it comes from.
Do the ampacity columns include the correction factors?: No. They are base table values: 30°C ambient, three or fewer current-carrying conductors and no termination limit. Apply the ambient factor and the conductor-count factor printed on the same sheet, then cap the result at the termination value for the equipment you have.
Can I use the IEC table for a North American job, or the NEC table in Europe?: No. The two sets are not interchangeable. They rest on different installation methods, reference conditions and grouping rules, so a number lifted from one cannot stand in for the other. Use the table that belongs to the standard your installation is inspected against — both are printed here so nothing has to be converted by hand.
Is the metric table just the AWG column converted?: No. A mm² to AWG conversion is geometry only: it compares cross-sectional areas. The IEC capacities depend on insulation, installation method, ambient temperature and grouping, which is why they are printed as their own table. For the conversion itself, use the mm² to AWG chart.
Can I print it, or hand it to someone else?: Yes. The sheet is free, needs no signup and prints on landscape A4 or Letter; the PDF is generated in the browser, so nothing is uploaded. If you pass it on, a link back to this page is appreciated and keeps the version current.
How are the values produced?: Every cell is computed by this site's calculation engine from registered constants rather than typed by hand, so the page, the PDF and the calculators cannot drift apart. The methodology page lists each source, its clause and its review status.

Sources, clauses and review status for every constant are on the methodology page.

Use the numbers in a calculator

Prefer the numbers in context? The correction-factor guide works through the same table step by step.