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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

This app has been updated by Apple to display the Apple Watch app icon.

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

Ratings and Reviews

3.7 out of 5
6 Ratings

6 Ratings

Mdarkness1988 ,

Needs updating for 64bit

From ios 11 releasing this year they are fully dropping 32bit apps and this app will then be invisible on the store.
Otherwise great app

Mason 41 ,


This app is excellent

Rivs101 ,

Doesn’t work???

Demo keeps resetting.

App Privacy

The developer, Cressall Resistors Ltd, has not provided details about its privacy practices and handling of data to Apple.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.


  • Family Sharing

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

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