Resistor Calc Toolbox

Quickly calculate LED resistor values, decode 4-band resistor color codes, or convert resistance values back into color bands.

Resistor Calc Toolbox is a simple, easy-to-use electronics utility for working with LEDs and 4-band resistors. Three calculators put commonly needed resistor information in one convenient app. LED Resistor Calculator Enter the supply voltage, LED forward voltage, and LED current to calculate the required resistance and minimum resistor power rating. Color Bands → Ohms Select the four resistor color bands to calculate the resistance value, tolerance, and tolerance range. Ohms → Color Bands Enter a resistance value and tolerance to find the corresponding 4-band resistor colors. Features • Three resistor tools in one app • LED resistance and power calculations • 4-band resistor color code decoding • Resistance-to-color-band conversion • Resistance tolerance range • Support for common resistor multiplier and tolerance colors • Clean, straightforward interface • Works on iPhone and iPad Whether you're working at the electronics bench, experimenting with LED circuits, or simply need a quick resistor reference, Resistor Calc Toolbox keeps the calculations close at hand. Important: Calculations are based on the values you enter and are provided as a design aid. Verify component values, ratings, tolerances, and suitability for your specific circuit before use.

I particularly like including our disclaimer at the bottom of the App Store description. It doesn't interfere with the sales pitch, but it's visible before purchase.