Dave is correct on actual
To figure true parlay odds you can take the return divided by the risk of all legs and then multiply those together to get what the odds should be.
So a -110 wager is 210(110 risk +100 if win)/110(risk)=1.909 a 3 teamer would be 1.909x1.909x1.909=6.957 to 1
if using a ML dog of say +180 280/100= 2.8 would be the factor
Damn I hope that's correct because I'm sure Shackfu is watching