Paid Vs Free (Lite) Versions

What is the difference between the Paid and Free (Lite) versions?

For most apps, the only difference is that the Free version has ads.

For Calculator HD Pro and Calculator Pro Elite, the paid versions also have 2 exclusive features available as In App Purchases (Widget and Multiple History Tapes).

Do I have to pay for the app on each device I own?

No, you only have to pay once and then you can download it again for free onto all of your devices.

The app is universal and works with both the iPhone and the iPad.

You can also share your purchase with others in your family if you have Family Sharing enabled on your account.

For more information about Downloading Previous Purchases and Family Sharing, please visit Apple at

Why do I keep getting ads after I paid for them to be removed?

The Paid version of the app is a totally separate app, so look for a new icon on your device without the word Lite on it.

Start using the Paid version from now on, and delete the Free version from your device so that you do not open it by mistake.

How do I restore an In App Purchase, or install it on another device?

From within the app, go to Settings, and scroll down to the bottom of the first page and tap Restore Purchases.

Calculator HD Pro & Calculator Pro Elite

How do I use the Widget (Calculator HD Pro & Calculator Pro Elite)?

The Widget can be accessed in your Today View or 3D Touch on the app icon.

Note that in iOS 14+, due to restrictions by Apple preventing buttons inside of home screen Widgets, the Widget can only be added to your Today View, and not your Home screen.

To add the Widget to your Today View in iOS 14+, watch this video:

To add the Widget to your Today View in iOS <14, and to see it in action, watch this video:

For more information on how to access widgets, visit Apple at

How do I use the Multiple History Tapes (Calculator HD Pro & Calculator Pro Elite)?

To see the in app purchase in action and how to use it, watch this video:

Convert Any Unit

Why is the unit conversion wrong (Convert Any Unit)?

There are two reasons why you may get a unit conversion that you do not expect:

1. You may have mistakenly selected the wrong category of unit. Make sure to select the correct category. When you are converting a Mass or a Volume unit, you usually want to select units in the same category for both the From and To unit. Some units have similarly named Volume and Mass versions. For example:

  • Volume fluid ounces (fl oz)
  • Mass ounces (oz)

It is possible to do a mixed category conversion between Mass and Volume or Volume and Mass in which case a material density is required as a third input. While you are searching for the second unit, the app will let you know if it is going to be a mixed category conversion by highlighting the unit category in Red instead of Green, and the unit conversion itself will have a material indicated (the default is water).

2. You may have mistakenly selected the wrong version of unit. Make sure to select the correct version. Many units have multiple versions of the same named unit. For example, the Volume unit of gallon (gal) has 3 different definitions (Imperial, US dry, and US liquid). If a unit has multiple version with the same name, the app will indicate the version of the unit by highlighting it in Red brackets at the end of the name of the unit:

  • gal (gallon) [Imperial]
  • gal (gallon) [US dry]
  • gal (gallon) [US liquid]

If you are not sure which unit you want, you can click on the Wikipedia links next to each unit in the app to learn more.