OK — been using this thing for maybe six months now and I keep coming back, so figured I'd say something since a mate asked me the other day. I'm based in the UK, generally stick to footie and the horses, small stakes, just so you know where I'm coming from.
The reason I started using it was genuinely pretty stupid — I couldn't ever figure out what an e/w return actually came to once you get five places instead of three. I'd just guess and then be surprised. These days I punch the numbers in first, every time, even the boring singles.
The single bet calculator tool is the one I use most — you drop in your stake, the odds and it spits out the return with no faffing, either odds format. Same tool covers the fiddly ones — acca and treble returns, lucky 15 and lucky 63, patents and yankees, honestly that's where I'd always lose track. If you fancy a poke about, it lives at lucky 63 bet — free, no signup.
What really changed how I bet was the geekier bits. There's an implied probability thing and it makes obvious how much the bookie's taking, and a kelly staking calculator — I use half kelly since full stakes are far too aggressive. Dutching calculator gets used a fair bit if I'm spreading across selections.
It's not perfect mind. Its design looks a bit basic — zero polish, looks like it was built by someone who cares more about maths than colours. On mobile it's fine though the acca grid need a bit of scrolling. There's nothing on the app store, just the site — doesn't bother me just flagging it.
So yeah. Doesn't cost anything, not plastered in adverts, does the job. If you even now adds it up in their head, have a look — saved me a fair few "wait, that's it?" moments.