Most small old houses only have a 100amp service panel, 4-5 bedroom, very large houses have a 200 amp panel. Now a days,with a small house, you should have a min of 150amp panel installed.
To answer you question, there is a main service panel calculation that is used,and goes by
the house as to get a service that will pass codes.
In residential wiring applications the most used is 14 gauge wire for light switches as long as the circuit breaker or the fuse is 15A. If your lighting circuit is on a 20A fuse/circuit breaker then you need to use 12 gauge wire
A ten-gauge wire is typically rated to carry around 30-35 amperes of current. It's important to consult the manufacturer's specifications or relevant electrical codes to determine the exact ampacity for a specific application.
A 6-gauge wire is commonly used for a 63 amp breaker in a residential setting. However, it's always best to consult with a licensed electrician to ensure the correct wire size based on your specific installation requirements.
The wire sheathing itself is usually marked. e.g. 14 CU 2 or 14/2 CU will indicate 14 gauge 2-wire (+ ground) copper (CU being the symbol for copper on the periodic table). For 15amp circuits you will likely has 14 gauge wire with most of that being 14/2 (Usually white, black, and bare copper).
Wire is not sized by voltage. It is sized by current measured in amps. Some common copper wire sizes and their current capacities are: 15 amps -- 14 gauge wire 20 amps -- 12 gauge wire 30 amps -- 10 gauge wire 40 amps -- 8 gauge wire
The recommended gauge for a 30 amp wire in a residential electrical circuit is typically 10 AWG (American Wire Gauge).
The recommended gauge for a 60 amp wire in a residential electrical installation is typically 6 AWG (American Wire Gauge).
The recommended gauge for a 70 amp wire in a residential electrical system is typically 4 AWG (American Wire Gauge).
The recommended gauge for an 80 amp wire in a residential electrical system is typically 4 AWG (American Wire Gauge).
The recommended gauge for a 30 amp wire in a residential electrical installation is typically 10 AWG (American Wire Gauge).
The recommended gauge for a 40 amp wire in a residential electrical circuit is typically 8 AWG (American Wire Gauge).
The recommended gauge for a 60 amp wire in a residential electrical system is typically 6 AWG (American Wire Gauge).
The recommended gauge of wire for connecting lights in a residential setting is typically 14 gauge.
The recommended gauge size for a 20 amp wire in a residential electrical circuit is typically 12 AWG (American Wire Gauge).
The recommended gauge for 18/4 thermostat wire in a residential HVAC system is typically 18 AWG (American Wire Gauge).
The appropriate gauge size for a 10 amp wire in a residential electrical circuit is typically 14 AWG (American Wire Gauge).
The recommended gauge of wire for electrical installations in residential buildings is typically 12.