Use this calculator to help select the correct wire size.

  You should never use a wire that is not suitable for the amperage that it will carry. The wire might possibly melt in a worse case scenario or overheat.

  However keep in mind that an outlet or receptacle rated for 50 Amps, doesn't mean that the equipment connected to that outlet requires 50 Amps.

Likewise simply because an appliance or device features a 6-50P or 14-50P plug doesn't mean that it will be drawing 50 Amps. 

  Inrush current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform, then level out drawing significantly less. 

•  Terms such as "Heavy Duty" and "Contractor Grade" are often used in product descriptions of electrical cords.
• The terms have no universal definition.
• Do not just buy an extension cord simply because the packaging states it's HEAVY DUTY and rated for INDOOR and OUTDOOR use.
• "Heavy Duty" is often used to describe 8/4 SEOOW Portable Cable but the term is just as likely to be used to describe 12/3 SJT Extension Cords. However there is a significant difference between those two cables. 

If you plan on using a maximum of 30 amps, you should use 10 gauge wire up to 100 ft. You should use 8 gauge wire for distances over 100 feet or when operating any continuous use items between 50 ft and 100 ft.

To safely use a maximum of 40 amps, you will need a wire gauge of 8. This will allow you to safely use items in your house such as an electric cooktop.  To use a maximum of 50 amps, you will need a wire gauge of 4. There are some electronic devices in our household that require only a maximum of 40 amps. However, there are some appliances that will need 50 amps, such as a washer or dryer. You can sometimes even use a wire size of 6 for 50 amps but the smaller the number on the gauge scale is the better. This is because the lower the number on the gauge scale is, the thicker and more durable the wire is. This is especially true if you plan on running the wire for more than 100 feet. 

A home refrigerator's power consumption is typically between 300 to 800 watts of electricity, or between 3 and 6 amps and about 120 volts. Importantly, refrigerators generally have a much lower "running" wattage than their stated average wattage – this is because they cycle on and off throughout the day.

Small window AC units (5,000 to 8,000 BTU) typically use 5 to 7 amps. Medium window AC units (10,000 to 12,000 BTU) often use between 8 to 12 amps. Large window AC units (14,000 to 25,000 BTU) can use anywhere from 12 to 20 amps or more.

Central air conditioners typically require higher air conditioner amperage due to their larger cooling capacity. A 2-ton central AC unit may draw around 15-20 amps. A 3.5-ton unit may require 25-30 amps. A 5-ton unit may need 30-40 amps.