PCalc is absolutely wonderful, both the Lite version and the paid version, and the Lite version has no banners, only an option in the settings to upgrade. It's

PCalc is absolutely wonderful, both the Lite version and the paid version, and the Lite version has no banners, only an option in the settings to upgrade. It's the second free calculator in my search results when I search for "calculator". Discoverability is not great but there are plenty of awesome apps on the App Store, some free but you have to be willing to pay if you want quality.