About BettingCalcs

Who Built This Site

My name is Derek Shaw. I spent three years as a sports data analyst at a regional sports media company, where I built models, tracked line movement, and ran numbers on everything from player performance to market efficiency. Before that — and during, and after — I've been a recreational sports bettor and poker player for over a decade. Not a professional gambler. A math guy who genuinely enjoys the analytical side of putting money on a game.

When I started looking for reliable, standalone betting calculators online, I kept running into the same two problems. First, the math was wrong — or at least sloppy. Expected value formulas applied without accounting for juice, Kelly criterion outputs that ignored fractional sizing, parlay calculators that didn't clearly display the vig baked into the odds. Second, most "free" tools were essentially sportsbook lead-gen pages. The calculator was secondary to the affiliate pitch. Before you could use the tool, you were being pushed toward a sign-up bonus.

I built BettingCalcs because I wanted one place with accurate formulas, no sign-up walls, no sportsbook sponsors, and no agenda beyond getting the math right. Every calculator on this site is free to use, and there's nothing to create an account for. The math stands on its own.

What This Site Covers

BettingCalcs currently offers six core calculators and a growing library of guides focused on the analytical side of sports wagering:

Parlay Calculator — Enter your legs, odds, and stake to see exact parlay payout and combined implied probability. Kelly Criterion Calculator — Optimal bet sizing based on your edge and bankroll. Expected Value (EV) Calculator — Calculate whether a given bet has positive or negative expected value over the long run. Arbitrage Calculator — Identify sure-bet opportunities across sportsbooks and compute the exact stake splits needed to lock in profit regardless of outcome. Odds Converter — Convert seamlessly between American moneyline, decimal, and fractional odds formats. Bet Profit Calculator — Calculate net profit and ROI on any straight wager.

The guides section covers foundational concepts: understanding expected value, how to read American odds, bankroll management principles, and what closing line value actually tells you about your betting process.

How the Math Works

Every formula on this site is sourced, tested, and verified against known outcomes before it goes live. The Kelly Criterion implementation uses the original formula published by John L. Kelly Jr. in the 1956 Bell System Technical Journal: f* = (bp − q) / b, where b is the net odds received on the bet, p is the probability of winning, and q is the probability of losing (1 − p). The EV formula adapts the standard expected-value framework used in probability theory: EV = (p × profit) − (q × stake).

Odds conversions use standard formulas: positive American odds convert to decimal via (odds / 100) + 1; negative American odds convert via (100 / |odds|) + 1. Fractional odds convert to decimal by dividing numerator by denominator and adding 1. These are the same conversions used by every major odds aggregator.

Before publishing each calculator, I ran the outputs against verified historical examples — known parlay payouts from sportsbook records, Kelly outputs matched against textbook examples, EV results cross-checked against hand-calculated figures. If the numbers don't match, the tool doesn't go live.

Get in Touch

I read every message that comes through the contact form. If you've spotted a formula error, have a question about how a specific calculation works, or want to suggest a calculator or guide topic, I want to hear from you. BettingCalcs is a one-person project — feedback from people actually using the tools is the fastest way to catch mistakes and figure out what to build next.

I won't respond to sponsorship or affiliate partnership inquiries. The independence of this site is the whole point.

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