OhmsLab: Ohms Law & Codes

The everyday electronics bench in your pocket. Solve Ohm's law, read resistor color codes, and size LED resistors in seconds, all on your iPhone.

WHAT IT DOES

• Ohm's law and power: enter any two of voltage, current, resistance or power and get the other two
• Resistor color decoder: 4, 5 and 6 band, with tolerance and temperature coefficient, drawn on a real resistor
• Find the colors for a value: enter a resistance and see the bands
• LED series resistor: from supply, forward voltage and current, with the nearest standard value and a power rating
• Series and parallel: combine any number of resistors, both totals at once
• Voltage divider: output voltage, current and power, plus a helper to size R2 for a target output
• Save any calculation to your bench and reopen it live
• Bench reference: the full color code table, SI prefixes and the Ohm's law relationships
• Copy any result, clean dark bench interface

PRIVATE BY DESIGN Everything you enter stays on your iPhone. No account, no cloud, no tracking.

FREE AND LIFETIME Free includes the Ohm's law and power solver and the full resistor color decoder, with unlimited saved calculations. The one time Lifetime unlock ($4.99 USD, pay once, no subscription) adds the LED resistor, voltage divider, and series and parallel tools, plus PDF and CSV bench sheet export.

Built for makers, students, repair techs, and anyone who keeps a soldering iron warm.

A planning aid for hobby and bench work. Check part datasheets and ratings before you build.