This isn't the first Christmas dinner I've cooked, but I don't eat meat and I get nervous about ruining the massively pricey meat the hoards want at Christmas.
I'd forgotten about this, what with the Covid Christmases and visiting the in laws last year.
Anyway - choose your meat, choose your rareness, choose your weight - the bbc will tell you how long to cook it. It's worked for me in the past, and is actually the same time as I'd calculated by hand from my Delia book.
Roast Timer
Ok, not actually an app