Alternate Lines Calculator
Translate a price on an alt line into break-even probability.
Enter American odds; the tool shows implied probability for that side.
Alternate Lines Calculator
Adjust inputs to see updated results.
Table of Contents
How to Use This Calculator
Enter American odds for Over and Under on the same alt line. The tool reports hold on the pair and a normalized over probability after removing the two-way imbalance scaling.
Same market
Both prices must be for identical line and book—mixing books breaks comparability.
Alt lines
Use the prices from the alternate spread/total tab you are evaluating.
Normalized over %
Shown as over share of the two-way implied mass—handy for comparing alts.
Hold readout
See how expensive that alt pair is versus a main line.
Two-Way Implied Split
The engine parses American prices to decimals, takes implied 1/d, sums, and computes hold. Normalized over probability rescales by the sum so the two sides partition 100%.
Examples
Example 1 — Balanced −110 / −110
Hold ≈ 4.76%; normalized over probability ≈ 50%—symmetric pricing.
Example 2 — Skewed alt
−130 / +110 shifts normalized over probability away from 50—see which side is cheaper after vig strip mentally.
Example 3 — Shop alts
Run the same alt at two books—lower hold with similar normalized prob can be the better ticket.
Frequently Asked Questions
The math path matches the player-prop page in this codebase—two American sides on one line.
It shows raw and normalized implied splits. Use fair odds for no-vig stripping.
Inputs are American-style as labeled. Convert decimals manually if needed.
Not supported—two outcomes only.
Half-point, Hold, Spread.
So you can see relative over/under belief after removing the two-way scaling factor inside this simple model.
