Tools you might need next
Calculate current-limiting resistor value and wattage for LED circuits from supply voltage, forward voltage, and desired current.
Calculate output voltage and resistor values for voltage divider circuits from input voltage, R1, R2, and load considerations.
Calculate RC circuit charge and discharge time constants, voltage curves, and time to reach a target voltage level in seconds.
Hold the resistor with tolerance band (often gold or silver) to the right. First bands are significant digits.
Significant digits form a number multiplied by the multiplier band.
R = (digit1 digit2 …) × 10^multiplier ΩGold is ±5%, silver ±10%, and brown on 5-band often means ±1% precision.
Updated: July 2026
Decode brown-black-red-gold as 1 kΩ ±5% before using in a prototype.
Generate 5-band code for a precision value when ordering is not immediate.
Practice reading bands on 4-band carbon film resistors in a classroom kit.
Gold or silver multiplier is rare on small values. Place tolerance on the right.
Verify critical values with a multimeter, especially in series power paths.
Read or generate resistor color codes instantly. Select 4-, 5-, or 6-band resistors to decode value, tolerance, and temperature coefficient.