[50% OFF] TechniCalc Scientific Calculator for iOS, iPadOS and macOS
It's available on iPhone, iPad, and macOS - and one purchase unlocks it on all platforms. It receives regular updates, and has done for over the over 6 years it's been available
For the next 24 hours, the app is 50% off from it's normal price of $7.99 ($3.99)
If you do take advantage of the offer, a rating and review in the App Store would be hugely appreciated. It really does make a huge difference!