How do I convert fractional odds to decimal?
Divide the fraction and add 1: decimal = (a/b) + 1. Example: 10/11 → 10/11 + 1 ≈ 1.91. Enter 10/11 in the fractional field and decimal updates automatically.
Odds Converter Calculator
Sync fractional, decimal, American & probability % in real time—one field updates all four
Content reviewed regularly for accuracy
By the OddsGPT Betting Tools team — sports betting math & odds education.
What is an Odds Converter?
An odds converter translates betting prices between formats used in the UK (fractional), Europe (decimal), the US (American moneyline), and implied win probability (%). Sportsbooks quote the same edge differently—this tool keeps you comparing apples to apples.
Enter any value and all four fields update instantly using standard bookmaker math. Use it to shop lines, sanity-check parlay legs, or feed fair prices into vig and EV calculators.
Core principle: Decimal odds O include stake return: profit = O − 1. Implied % = 100/O. Example: 1.91 decimal (−110) → 52.38% implied. Fractional 10/11 matches the same price.
Convert Odds Instantly
Edit fractional, decimal, American, or probability %—the other three fields sync automatically.
Profit/stake fraction, e.g. 10/11 or 3/2
Total return per $1 staked, e.g. 1.91
Moneyline, e.g. −110 or +150
Implied win chance 0–100%
How to Use This Odds Converter
Type in any format. The calculator converts using industry-standard formulas and rounds for display. Invalid fractions or probabilities outside 0–100% clear the other fields.
- Fractional odds: Enter like 10/11 (profit per unit staked)
- Decimal odds: Enter total return per $1, e.g. 1.91
- American odds: Enter −110 favorites or +150 underdogs
- Probability %: Enter implied % between 0 and 100
Important: Posted probability includes vig. For fair (no-margin) prices on two-way markets, convert here then use our vig or no-vig calculators.
Tips & Best Practices
- Decimal for EU books, fractional for UK racing, American for US spreads—convert once, compare everywhere.
- Higher implied % = shorter odds = book prices the outcome as more likely.
- Before building a parlay, convert each leg to decimal to verify combined payout math.
- Two −110 sides sum to ~104.76% implied—the extra 4.76% is vig, not true probability.
- If your model beats implied % after de-vigging, screen with our EV calculator before staking.
- Parlay example: legs at 1.91, 2.10, 1.75 → combined decimal 1.91×2.10×1.75 ≈ 7.02 (+$602 profit per $100 stake if all win). Convert each leg here first.
Odds Conversion Formulas (Fractional, Decimal, American)
Decimal O: implied p% = 100/O. American favorite (negative): p% = |odds|/(|odds|+100). American underdog (+): p% = 100/(odds+100). Fractional a/b: p% = b/(a+b)×100. Decimal from fractional: O = a/b + 1.
Payout profit on a $100 stake: decimal profit = 100×(O−1); American +odds profit = 100×(odds/100); American −odds profit = 100×(100/|odds|). Fractional a/b profit = 100×(a/b).
Decimal odds \(O\) and implied probability \(p\) as fraction:
\[ p = \frac{1}{O}, \quad O = \frac{a}{b}+1, \quad p\% = \frac{b}{a+b}\times 100 \]
Reverse: \(O = 100/p\%\). Fractional \(a/b\) → \(O = a/b + 1\).
Worked Example: −110 to All Formats
Standard US line −110 on one side of a spread or total.
Step-by-step: −110 → all formats
- Step 1 — American: Start with −110 (risk $110 to win $100).
- Step 2 — Decimal: O = 100/110 + 1 = 1.91 (total return per $1).
- Step 3 — Fractional: Profit/stake ≈ 100/110 → 10/11.
- Step 4 — Probability: p% = 100/1.91 ≈ 52.38% implied.
Matches fractional 10/11 and decimal 1.91. Two −110 sides → ~4.76% vig—use our vig calculator.
Real-World Market Example: NFL Point Spread
Posted lines on a typical NFL spread look even—but the book still charges margin on both sides. Convert each price here, then strip vig to see what a fair market would look like.
| Market (posted) | Side | Line & price | Decimal | Implied % |
|---|---|---|---|---|
| NFL spread (retail) | Kansas City Chiefs | −3 (−110) | 1.91 | 52.38% |
| Buffalo Bills | +3 (−110) | 1.91 | 52.38% |
Each −110 → decimal 1.91, implied 52.38% per side. Combined implied ≈ 104.76% → about 4.76% vig on the market.
Fair odds after removing vig (no-vig baseline)
Normalize both 52.38% implied probabilities to 50% each. Fair American prices land near −102 / −102 (decimal ~1.98)—not +100, because books round posted −110 to 1.91. Use our vig calculator on −110/−110 to reproduce this in one step.
| Side | Fair (no-vig) | Line & price | Decimal | Implied % |
|---|---|---|---|---|
| Chiefs −3 | Fair (no-vig) | −102 | ~1.98 | 50.0% |
| Bills +3 | Fair (no-vig) | −102 | ~1.98 | 50.0% |
Soccer moneyline snapshot (Premier League)
Example: Liverpool −140 / Draw +260 / Everton +380 on a 1X2 market. Convert each leg to implied %—the three-way total often exceeds 106–110% because books price draw and underdog with extra margin. Three-way de-vig needs our no-vig calculator.
Sportsbook Margins: Sharp vs Recreational Books
Not all posted odds carry the same margin. Sharp sportsbooks such as Pinnacle (where legally available) often run tighter two-way NFL/NBA spreads—sometimes near 2–2.5% vig on liquid games—because they welcome informed action and adjust lines quickly.
Recreational (soft) books—typical US retail apps and many EU brands—more often post −110/−110 (~4.76% vig) on spreads, with wider prices on props, same-game parlays, and alt lines. Converting odds to implied % is how you spot when a soft book is charging 6–10%+ on a market Pinnacle prices at 3%.
Betting exchanges (e.g. Betfair) charge commission on net winnings—effective hold often lands near 2–5% on liquid match odds when commission is ~5%, but thin markets can still be expensive. Always convert the back/lay prices you actually get, not headline “exchange = cheap” myths.
Why Lower Vig Matters for Long-Term Profitability
Vig is not a one-time fee—it raises the win rate you need to break even on every bet. Reducing bookmaker margin from ~5% to ~2% dramatically lowers long-term break-even requirements, which is why serious bettors line-shop and prefer sharp books when available.
On a standard −110/−110 market you must win about 52.4% of bets just to break even (because you risk $110 to win $100). At reduced −105/−105, break-even drops to about 51.2%. That ~1.2 percentage-point gap compounds over thousands of wagers.
| Two-way line | Approx. vig | Break-even win % | Long-term impact |
|---|---|---|---|
| −110 / −110 (retail standard) | ~4.76% | 52.4% | Need >52% accuracy on flat −110 plays—hard for most models without real edge. |
| −105 / −105 (reduced juice) | ~2.38% | 51.2% | ~1.2 pts easier than −110—meaningful over a season of volume. |
| Sharp book (~−104/-104 equivalent) | ~2–2.5% | ~51.0–51.2% | Why pros track Pinnacle closing lines—lower tax on edge. |
−110 / −110 (retail standard)
52.4%
−105 / −105 (reduced juice)
51.2%
Sharp book (~−104/-104 equivalent)
~51.1%
Illustration: at 1,000 bets per season, improving break-even from 52.4% to 51.2% is roughly 12 extra winning bets worth of cushion—before counting any handicapping edge. Convert posted prices here, compare vig across books, then size only +EV spots.
Industry Margin & Hold Benchmarks (Illustrative)
Figures below are educational ranges seen in market discussions—not live quotes. Always convert the exact odds your book offers today.
| Market type / book style | Typical vig / overround | Indicative hold % | Notes |
|---|---|---|---|
| Pinnacle — NFL/NBA spread (liquid) | ~2.0–2.5% | ~2.0–2.4% | Sharp benchmark; lines move on pro money |
| US retail — main spread/total | ~4.5–5.0% (−110/-110) | ~4.3–4.8% | Default −110 juice; promos may briefly improve |
| Soft book — player props / alts | ~8–15%+ | ~7–14% | Higher margin; convert before betting |
| Exchange — liquid match odds (~5% comm.) | ~2–5% effective | Varies by liquidity | Back/lay spread + commission on wins |
| Historical hold — Super Bowl props (retail) | often 10%+ | ~9–12%+ | Retail books reported double-digit hold on novelty props in past big games—why converters matter before casual Super Bowl bets. |
Sources: aggregated industry commentary, hold reports, and bettor education literature. Margins change by sport, jurisdiction, and event liquidity.
Understanding Betting Odds Formats by Region
Fractional (UK): Shows profit relative to stake—10/11 means win $10 per $11 risked. Decimal (EU/AU): Total return per unit, including stake. American (US): Moneyline based on $100 baseline—negative favorites, positive underdogs.
Probability % is format-agnostic—ideal for comparing the same outcome across books. For deeper implied-probability theory, see our implied probability calculator.
Quick Example: +150 Underdog
+150 → decimal 2.50 → implied 40% → fractional 3/2. Profit on $100 stake = $150 at +150.
Smarter Workflow After Converting
Measure book margin with the vig (juice) calculator on two-way prices.
Test edge with the expected value calculator after you know fair implied %.
Combine legs via the parlay calculator or hunt locks with the arbitrage calculator.
Related Betting Calculators
Key Takeaways
Always convert to one format (or implied %) before comparing books. Remember vig inflates implied totals on standard markets. Pair this converter with vig, EV, and parlay tools—conversion alone does not prove +EV. Bet responsibly.
Responsible Gambling
Odds tools are for education. Gambling risks loss and addiction. Set limits, take breaks, never chase losses.
Resources: BeGambleAware, NCPG (US), GamCare (UK).
See today's AI football predictions →
Frequently Asked Questions
How do I convert American odds to decimal?
Positive American: decimal = (odds/100) + 1. Negative: decimal = (100/|odds|) + 1. Example: +150 → 2.50; −110 → 1.91.
How do I convert odds to probability percentage?
From decimal O: probability % = 100/O. From −110 American: 110/(110+100) ≈ 52.38%. Enter any format here—the probability field syncs in real time.
What is the difference between decimal and American odds?
Decimal shows total return per $1 staked (1.91 = $1.91 back per $1). American shows profit on a $100 bet baseline (+150 wins $150, −110 risks $110 to win $100). Both describe the same price—only the display differs.
Why do converted probabilities add up to more than 100%?
Each posted price includes bookmaker vig. On −110/−110, each side is ~52.38%, totaling ~104.76%. The excess is margin—not extra win chance. Use our vig calculator to see fair no-vig prices.
Can I convert probability % back to odds?
Yes. Enter probability % and fractional, decimal, and American fields update. Math: decimal = 100/p%. Example: 40% → 2.50 (+150).
Is this odds converter free?
Yes—OddsGPT's odds converter is free with no signup. Results use standard sportsbook formulas; minor rounding may differ by book.
Odds converter vs implied probability calculator—what's the difference?
This page focuses on fast four-way sync (fractional, decimal, American, %). Our implied probability calculator adds deeper vig/overround education—use both: convert here, then analyze margin on the implied or vig pages.
Why do sharp bettors care about Pinnacle closing lines?
Pinnacle is widely used as a sharp reference because it accepts high limits on liquid markets and posts tighter margins than most retail books. Converting closing prices to implied % lets you measure closing line value (CLV)—beating the closing implied % is a strong long-term skill signal.
