Fuse Size Chart

Automotive blade fuses follow a universal color code by amperage, so you can identify a rating at a glance. This applies to standard (ATO/ATC), mini, and low-profile blade fuses alike.

Amperage Color
2 A Gray
3 A Violet
5 A Tan
7.5 A Brown
10 A Red
15 A Blue
20 A Yellow
25 A Clear / natural
30 A Green
40 A Amber / orange
Never upsize a fuse. A fuse protects the wiring, not the device. Replacing a 15 A with a 20 A lets the wire overheat before the fuse blows — a fire risk. Match the rating exactly.

Size a circuit with the Fuse Size calculator in the automotive calculators.

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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.