How many amps can 8mm wire carry?
8mm Twin core automotive cable (8B&S) - Rated to 60- 75 Amps.
RULES OF THUMB
“Twelve-gauge wire is good for 20 amps, 10-gauge wire is good for 30 amps, 8-gauge is good for 40 amps, and 6-gauge is good for 55 amps,” and “The circuit breaker or fuse is always sized to protect the conductor [wire].”
Depending on the voltage, the 8 AWG copper wire can carry anywhere from 480 watts (12V circuit) to 9600 watts (240V circuit). Under the same conditions, the ampacity of the 8 AWG aluminum wire is 40A. Accounting for NEC 80% rule, this means that a 8 AWG aluminum wire can handle up to 32 amps of current.
In short, the perfect wire size for most 30 amp services is the #8 AWG wire with 50A ampacity. This is the common size wire for 30 amps 240 volt service, 30 amp 220 volt service, and so on.
8-gauge copper will handle fifty amps, but it will get hot (75 degrees C).
For 60 ampere breakers, electricians and professionals suggest using a wire size gauge ranging from 6 AWG to 4 AWG. All household wires have a rating of at least 600V, so only amperage really matters when it comes to determining wire gauge. Therefore, the wire size for 60 amp 220v, for example, is still 6 to 4 AWG.
All Things Considered. Size 8 wire can handle anywhere between 40 and 55 amps and the aluminum versions can handle 40 to 45 amps. This type of wiring has a lot of applications both in commercial and residential buildings.
A basic rule of thumb is this. For up to 500 watts RMS, 8 gauge is sufficient. In the 500 – 1000 watt RMS range, you want to run 4 gauge. From 1000 – 1500 watts RMS you should be running 2 gauge.
For a maximum of 40 amps, you'll need a wire gauge of 8. Many electric cooking appliances require 40 amps such as electric cooktops.
Since 8 gauge wires can capably carry 40 amperes, we can determine that the proper size breaker is at 50 A.
Does thicker wire mean more power?
The thin wire will conduct electricity, but there is more electrical resistance. The thicker wire is like the four lane highway. There's a lot less electrical resistance, and as a result, that light bulb burns brighter because more electricity can reach it.
Looking up the brand of breaker that's in my panel, #8 wire fits the 20 amp breaker just fine (it is the largest size that breaker is listed for, but no adapter needed.)

Any circuit fused for 30 amps must use a minimum of 10 ga copper or 8 ga alu. Longer runs may require an upgrade of wire size.
If a wire gauge is “too big” then it is a lot more expensive and is harder to bend, as well as more difficult to attach with wire nuts or to switches.
6 AWG wire with 65A ampacity (just right).
However, in almost all cases, the correct 50 amp wire size is 6 AWG with 65A ampacity. That is true for any voltage; 12V, 110V, 115V, 120V, 220V, 240V, you name it.
When you plug a 30 amp adapter into a 50 amp breaker at the pedestal, the 50 amp breaker will only pop if the amperage goes beyond 50 amps. The problem here is that these adapters and the power cord for your RV are only rated at 30 amps.
60 amp wire size is either 6 AWG or 4 AWG wire (AWG stands for American Wire Gauge; standard wire sizing is the US) for 220V voltage. An amateur will use a 6 AWG wire size for 60 amp 220V. A professional will always use 4 AWG wire size for 60 amp 220V.
What size wire should I use for a 60 amp subpanel? You can get away with 6 AWG when you have a short run of wire, however, due to voltage drop, if you ever decide you want to go more than 100 feet then a 4 AWG is the size you should choose.
The rule of thumb is to go up one size larger if you plan on running the recommended wire size over 100 feet. This means that if you are planning on running 8-gauage wire for a 40 amp breaker over 100 feet, you should go to 6-gauge wire.
For 70 amp, the right wire is either a gauge 3 aluminum or a gauge 4 copper.
What wire do I use for 40 amps?
For a 40 amp, you need an 8-gauge wire. For a 20 amp, you will need a 12-gauge wire. For 60 amp, the correct wire size is 4. The right wire size for 50 amp is a 6 for both your breaker & circuit.
Generally speaking a 45 amp breaker requires a wire size of #6 AWG or larger to handle the current.
How do you determine cable wire size? Divide the voltage running through the cable by your target current. If, for instance, 120 volts will act on the cable, and you want 30 amps to run through it: 120 / 30 = 4. This is your target resistance, measured in ohms.
Choosing Electrical Wire Size
18-gauge are used for low-voltage lighting and lamp cords in 10 amps. 16-gauge are used for light-duty extension cords supporting 13 amps. 14-gauge are usedfor light fixtures, lamps, lighting circuits with 15 amps.
To determine what gauge wire you need, consider the carrying capacity and the amount of current the wire needs to conduct (measured in amperage or amps). Wire gauge is directly related to how many amps you need to run through it. The distance you need the wire to go can also impact the gauge of wire you need.