My Texas Instruments DMS : DD function has been just the ticket for the last 18 years!
Amazed that you guys get the chance to fly often enough these days to need to use a calculator at all.
Top tip - keep your log book away from the sqn and enter your trip times on the same day. Then you won't have to fight for the auth sheets at the end of the month!! The biggest log book snags come from waiting for some minor cog to cross-check them and then waiting for them to come back after some wheel has signed them.