Keep the line bet and odds bet mathematically separate.
That distinction explains why adding fair odds lowers the weighted edge on total action without changing the cost of the required line wager.
Cost tools
What these craps tools work out
The Pass Line plus odds calculator keeps the two parts of a line bet apart: the Pass Line wager carries a 1.41% house edge (7/495), and the odds bet behind it pays true odds, so it carries none. The bet cost calculator turns a bet’s edge into dollars over as many bets as you enter.
A worked example
Put $10 on the Pass Line and $50 in odds. The expected loss stays at about 14 cents, the cost of the $10 line bet, while the money at risk grows to $60, so the edge on the combined amount falls to 0.24%. The odds didn’t make the line bet cheaper; they added money that costs nothing. Now bet $25 on Place 6, resolved 50 times: $1,250 at 1.52% is about $18.94 expected.
What they assume
Edges are per bet resolved, odds limits vary by table (3-4-5x is common), and neither tool simulates a full session. Start with how to play craps, then the craps bet map, place vs buy and dice probabilities.