Electrical service entry masthead (C) Daniel Friedman Electrical Service Entry Cable & Branch Circuit Wire Size FAQs

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Electrical wire sizes & gauges vs Amps-ratings FAQs:

Questions & answers about electrical wire sizes, ampacity rating, run length, usage.

This article series gives Tables of Electrical Service Entry Cable Sizes, Electrical Circuit Wire Diameters, Circuit Ampacity, Allowable Voltage Drop, & Wire Size Increase based on Run Length assist in determining the electrical service size or other required electrical wire sizes at buildings.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Electrical Wire & Service Entry Cable FAQs

Close-up measurement of the diameter of a #14 copper electrical wire (C) Daniel Friedman

These questions and answers about electrical wire sizes and servicve entry cable sizing were posted originally at SE CABLE SIZES vs AMPS - be sure to review that article.

On 2018-06-14 by (mod) - actual wire size measurement


You are so right

thank you for your careful reading I'll correct the text

On 2018-06-14 by Max

The SE CABLE SIZES vs AMPS article says the photo looks like "2.5 mm" wire, but it clearly looks like 1.5 mm.

On 2018-05-15 by (mod) - match wire size to amps loading for the circuit


Take a look at the data tag on your electric motor: find the voltage and the AMPERAGE that the motor requires. That will let you find the right wire size in the tables in this article series.

On 2018-05-15 by Magesh Kumar Srinivasan

For 7.5 HP Motor, 720 electrical wire is enough or what is to be used. please advice

On 2018-05-04 by (mod) -


No. 1 AWG copper

On 2018-04-28 by lee

what is the max size wire that will fit in a 100 amp breaker

On 2018-03-12 by Mike Burg

Can I use 2/0 aluminum service entrance cable for a small two family that has 100 amp panels for each unit?

On 2018-01-25 by (mod) -


The tables at AMPS & SEC SIZES note that using #10 copper you can run up to 200 ft. and be within acceptable voltage drop.

On 2018-01-25 by Dave

Need to run a direct burial line from a 200 amp box in my home out 200 ft to end I need one or 2 receptacles.this line is primarily for a 3 hp 26 amp motor to operate a car big concern is voltage drop..will use aluminum wire as I understand it is price thank you

On 2018-01-17 by Anonymous

What size wire and protection conduit can i use in 720.5 ampere?

On 2017-12-14 by saddiii

Total types of cables and wd current ratting

On 2017-10-02 by Brian

What size wire to use to hook up a 220 well pump at 150 ft

On 2017-06-25 by Anonymous

The table of voltage drops, is it in feet or metres?

On 2017-05-31 by (mod) - 2 conductors = 2 wires, probably 1 hot, 1 neutral

Thanks for asking, John as it helps me see where we need to clarify our text. But in this case I don't see the exact phrase you use

1 pair 16, 2 conductor 14

in our articles.

In general, in electrical talk,

2 conductors = 2 wires, probably 1 hot, 1 neutral

16 refers probably to the wire size or gauge - #16 or 16 gauge (which you wouldn't use for a residential 120VAC light or receptacle circuit)

15 probably refers to #14 or 14 gauge wire, typically used on a 15 amp circuit in buildings

On 2017-05-31 by John

Sorry, 1 pair 16, 2 conductor 14?

What does 1 pair 16, 2 conductor 4 mean?

On 2017-04-21 by Geoffrey

what size of the cable to use when connecting a 37kw machine?

On 2017-04-20 by Jon

I have a bell to install in a warehouse. It is 12v, .125A and needs to be 50' from the receiver.
What gauge wire should I be using?

On 2017-04-08 by (mod) - Dedicated Electrical Circuit


We call these, or the National Electric Code (for U.S. readers) calls these "Dedicated Electrical Circuits"

Heavy-usage appliances like an electric clothes dryer or water heater will have their own electrical circuit and breaker or fuse

Critical-use appliances, even though not using high wattage may also have their own circuit for reliability, such as refrigerators that we don't want going off because something else on the same circuit caused and overload.

Electrical expert Mike Holt and others point out that:

In the U.S. the National Electrical Code, since (I think) 1999, section 210.11(C)(2) requires one dedicated 20 amp branch circuit for receptacle outlets in the laundry area. This circuit is not dedicated for only the washing machine, all receptacle outlets installed in the laundry area can be on the laundry circuit.

GFCI (ground fault circuit interrupter) protection may also be required, e.g. for electrical receptacles near a laundry sink.

On 2017-04-08 by Terri

Do you have to have separate circuits for all house appliances like washer n dryer

On 2017-03-22 by (mod) -

Thanks for the question Amyan.

In one of the tables above I give actual "normal" diameter of various wire gauges.

One can sometimes see the wire gauge or size printed on the insluating jacket
One can guesstimate the wire gauge by the overall conductor dimension, but that's just approximate as insulation thicknesses vary depending on the wire type and rating.
One can also use a simple micrometer or measuring gauge to measure the thickness of the metal wire itself.

On 2017-03-22 04:02:13.709797 by Amyan

How do you find the diameter of wire

On 2017-03-17 15:24:09.490597 by (mod) -

Yep. We're a Two Harbors MN bunch ourselves.

On 2017-03-17 02:58:57.216113 by Mike white

Thank you. I figured I was good. Minnesota is throughout.

On 2017-03-16 16:40:19.069096 by (mod) -

That sounds right, Michael. The breaker in the panel is only protecting wiring that is "downstream" from that point. So the wire between the overhead or underground service point and the panel is, in effect, not protected by that breaker in any event. Using a larger diameter wire in that location than would be required by the panel ampacity is always safe.

On 2017-03-16 05:40:03.804719 by Michael White

I have a outdoor amusement concession trailer and I am changing the main breaker from 200 to 100amps can i get away with keeping the 3/0 125 ft .lead line and pass the electrical requirements for Minnesota's inspection.

On 2017-03-10 21:34:04.398565 by Martin

If I have a 600A incoming service...what would be the size of the conduit and the size of the wire and how many wires

On 2017-01-28 06:36:33.438383 by Joshua

What size of 4core amould cable is appropriate to install a 350kva 3phase generator at a 45meter distance.

On 2016-06-27 13:51:05.916490 by (mod) -


Please see our instructions on how to print any InspectApedia page nicely formatted, found at

On 2016-06-27 04:30:14.149759 by Mahboob

This is the good page & very helpfulness its need Down loaded page

On 2016-03-22 04:59:52.201083 by Alan Firby

I am trying to find out how much load that aerial aluminium 7/4.75 conductor is good for

On 2016-02-09 16:45:33.911946 by (mod) -

JD I've added tables and content to the article above to address increasing the wire size for long runs.

For an SEC, rather than simply applying the rule of thumb to increase the wire size for each 100 ft of run, I suggest that you need to consult an electrical engineer who will consider the voltage drop and specify the wire size. Otherwise your cost may be unnecesssarily high.

On 2016-02-09 by JD

What size wire do i need to run from a 200 amp pole service to a house 450 feet away?

On 2015-08-14 by paul

You produce a great information.


(Nov 23, 2015) Anonymous said:
In the wire size table below give the typical diameter of #14 copper wire as 2.05 to 2.32 mm or about 0.081 - 0.092 inches
Table reads .
#14 0.073- .064 / 1.84-1.
#12 0.092-0.081 / 2.32-


(Jan 27, 2016) Carl said:

I’m studying on my own to become a home inspector. With that said after trying to interpret what this article is trying to convey to me and I’m left a bit confused and hoping you could clear somethings up.
I get MAX AMP Allowed according a specific wire size for branched circuit wiring; however, what I’m confused about is the Service Conductor Wire sizes. Is it a separate set of wire/amp ratings then mentioned for the Max Amp Allowed for branched circuit wiring?

When comparing Service Conductor Wire Size with the fuses (or) breaker I’m getting confused.

Here’s an example of what I’m referring to:
(Service Conductor Wire Size)
100 AMP Breaker… (#4 copper wire) …. #2 Aluminum wire

(MAX AMP Allowed – Branched circuit wire sizes)
#4 Wire gauge… 70 amps (CU) … 45-50 amps (AL)

So, am I to read that as there has to be an additional 30 amps pushed through that wire before the breaker pops?

Wouldn’t the #4 wire burn out before the 100 amp rating of the breaker? This is where I’m getting confused.


Continue reading at SE CABLE SIZES vs AMPS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see SIZE of WIRE REQUIRED for ELECTRICAL RECEPTACLES for receptacle circuits and similar wiring situations

Or see these

Articles on Determination of Ampacity & Voltage at Building Electrical Services

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