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Ohm's law and the power law describe the relationship between the following four electrical entities:


Current..........Amps.....A, I
Resistance...Ohms.....Ω, R

Ohm's law: Voltage = Current x Resistance
Power law: Power = Voltage x Current

Set any two, and the other two can be calculated.

This application allows you to continually lock one parameter and input another, enabling rapid "what-if" recalculation.

Use the keypad to enter a value then tap on the parameter you want to set. It is now fixed, as shown by the padlock symbol.

Enter another parameter and the remaining two are calculated. The most recently entered parameter becomes the new fixed one.

You can alter which parameter is fixed by tapping it when the input box is empty, or by dragging the padlock to it.

You can 'Freeze' a parameter with a long press until it changes colour. Now alter any of the other three as required. To unfreeze, with the input box empty, tap any other parameter.

The value of the fixed parameter may not be changed. If you attempt to do so, the padlock will flash. In this case, fix another parameter first.

Available in the following Languages:
English, French, German, Swedish, Russian, Polish, Spanish, Italian, Chinese (Traditional & Simplified).

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If you find any errors, or have any suggestions, please email us the details & we will address them!


What’s New

Version 1.7

Latest iOS support(64 Bit). Minor UI improvements.

Ratings and Reviews

3.7 out of 5
3 Ratings

3 Ratings

Mason 41 ,


This app is excellent

Rivs101 ,

Doesn’t work???

Demo keeps resetting.

Pete & Phyll ,

The best Ohm's Law calculator by far

An intuitive, well laid out and easy to use calculator for voltage, current and power work. The interface makes it simple to 'juggle' the circuit variables until you get the combination you want. The stand-out feature is that for "what if" calculations you don't need you to re-enter the data every time you change one variable, unlike most of the other Ohm's Law apps that I've tried. Highly recommended.


Cressall Resistors Ltd
1.6 MB

Requires iOS 8.0 or later. Compatible with iPhone, iPad and iPod touch.


English, French, German, Hindi, Italian, Polish, Russian, Simplified Chinese, Spanish, Swedish, Traditional Chinese

Age Rating


  • Family Sharing

    Up to six family members will be able to use this app with Family Sharing enabled.

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