Fuse Selection Calculator

Calculate minimum fuse rating, ambient temperature derating factor K_T, and surge withstand compliance based on IEC 60127 and UL 248.

Fuse Speed / Characteristic

Fast-acting (F / Fast Blow) Time-lag (T / Slow Blow) Medium-acting (M)

Fast-acting: Resistive loads with no inrush (LEDs, precision ICs)

Normal Load Current I_load (A)

Inrush Surge Multiplier (× I_load)

Inrush Duration (ms)

Ambient Temperature (°C)

Safety Margin Factor Recommended: 1.25–1.5 (IEC 60127 min is 1.25)

Results

Formulas

Min Rating = I_load × Safety Margin

Temp Derating: K_T = 1 + 0.004 × (T - 23°C)

Adjusted Rating = Min Rating / K_T

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