# Learn odds, payouts and market arithmetic

Follow a worked learning path through odds formats, margin, parlays and conditional returns. Use the free calculators with your own inputs, then inspect the assumptions.

Canonical page: https://getoddsapi.com/learn

## Free API key

Get a free GetOdds API key: **1,000 requests per UTC day and 60 per minute, no card**. One key covers REST and the hosted MCP server.

Sign up: https://getoddsapi.com/sign-up?ref=ai-claudebot

## Quickstart

1. Create an account at https://getoddsapi.com/sign-up?ref=ai-claudebot, open https://getoddsapi.com/dashboard and issue a key with the sources you need (draftkings, fanduel, betrivers, prizepicks or underdog). Keep it in a server environment variable named GETODDS_API_KEY.
2. Read current DraftKings NBA spreads with curl:

```bash
curl --fail-with-body "https://getoddsapi.com/api/v1/odds?sport=NBA&market=spread&fresh_only=true&limit=50" \
  -H "Authorization: Bearer $GETODDS_API_KEY"
```

3. The same request in Python (standard library only):

```python
import json, os, urllib.request

req = urllib.request.Request(
    "https://getoddsapi.com/api/v1/odds?sport=NBA&market=spread&fresh_only=true&limit=50",
    headers={"Authorization": "Bearer " + os.environ["GETODDS_API_KEY"]},
)
with urllib.request.urlopen(req) as res:
    rows = json.load(res)["data"]
for row in rows:
    print(row["away"], "at", row["home"], row["side"], row["line"], row["american"], row["observed_at"])
```

4. Check `observed_at`, `age_seconds` and `stale` on every row before using a price. Full reference: https://getoddsapi.com/docs

## Use with Claude (MCP)

```bash
claude mcp add --transport http getodds https://getoddsapi.com/api/mcp \
  --header "Authorization: Bearer $GETODDS_API_KEY"
```

The MCP tools follow the key's source grants and share its allowance. Setup guide: https://getoddsapi.com/use-with-claude

## Pricing

| Plan | Allowance | Price |
| --- | --- | --- |
| Free key | 1,000 requests a day, 60 a minute | $0, no card |
| Developer Bundle | 10,000 requests or credits a month on each of four sources | $149 a month |

Free development allowance: 1,000 requests per UTC day and 60 per minute per account, with no payment step. Paid: the Developer Bundle at $149 per month, with 10,000 monthly requests or credits on each of four sources.
Details: https://getoddsapi.com/bundle

## Guide


Canonical: https://getoddsapi.com/learn
Reviewed: 2026-11-07 UTC

Follow a worked learning path through odds formats, margin, parlays and conditional returns. Use the free calculators with your own inputs, then inspect the assumptions.

## Start with what a quoted price means

Decimal odds describe total return per unit staked when a selection wins. American and fractional odds express the same price differently. For example, +150, 2.50 and 3/2 describe a $25 total return from a winning $10 cash stake, before fees or deductions.

The reciprocal of a decimal price is its quoted break-even rate. It is not a measured chance of winning. Keep that distinction visible whenever you turn a price into a percentage.

- [Odds converter](https://getoddsapi.com/odds-converter): Compare American, decimal and fractional formats.
- [Implied probability calculator](https://getoddsapi.com/implied-probability-calculator): Convert a quoted price into a break-even percentage.
- [Implied probability glossary](https://getoddsapi.com/glossary/implied-probability): Read the definition and worked examples.
- [Odds calculator](https://getoddsapi.com/odds-calculator): Separate total return from net profit.

## Check the whole market before removing margin

A single quoted outcome does not reveal the margin of the whole market. Compare mutually exclusive, exhaustive outcomes with the same event, period, line and settlement rules. An incomplete set of outcomes can make the resulting arithmetic misleading.

The no-vig tools compare alternative assumptions about how margin is distributed. Their outputs are model probabilities, not verified forecasts. Theoretical hold is also distinct from a sportsbook’s realized revenue.

- [No-vig calculator](https://getoddsapi.com/no-vig-calculator): Compare multiplicative, additive, power and Shin models.
- [Bookmaker hold calculator](https://getoddsapi.com/hold-calculator): Inspect implied probability sum, overround and theoretical hold.
- [Vig glossary](https://getoddsapi.com/glossary/vig): Understand what margin calculations do and do not measure.
- [No-vig glossary](https://getoddsapi.com/glossary/no-vig): Review the assumptions behind removing margin.

## Combine selections without hiding correlation

Multiplying decimal prices gives the arithmetic of independently priced parlay legs. Every active leg must win for the stated return. A voided leg contributes a multiplier of one under the calculator’s refund assumption; actual settlement rules can differ.

Selections from the same game may be correlated. Their individual prices do not determine a sportsbook’s combined same-game price. Use the quoted combined price when the sportsbook supplies one, and keep teaser rules and bonus-bet stake treatment explicit.

- [Parlay calculator](https://getoddsapi.com/parlay-calculator): Calculate a combined price and conditional return.
- [Round-robin calculator](https://getoddsapi.com/round-robin-calculator): Inspect the number of combinations and total stake.
- [Same-game parlay calculator](https://getoddsapi.com/same-game-parlay-calculator): Start from a quoted combined price.
- [Teaser calculator](https://getoddsapi.com/teaser-calculator): Use the actual quoted teaser price and stated rules.
- [Bonus-bet calculator](https://getoddsapi.com/bonus-bet-calculator): Account for whether the original stake is returned.

## Separate a probability assumption from a decision

Expected-value and Kelly calculations depend on a probability supplied by the user. A confident-looking output cannot fix an inaccurate probability estimate, and a market’s implied percentage is not automatically that estimate.

Hedging, arbitrage and closing-line calculations also depend on comparable contracts, available prices, limits and settlement assumptions. The tools are arithmetic aids; they do not confirm that a live opportunity exists or that a proposed stake is suitable.

- [Expected value calculator](https://getoddsapi.com/expected-value-calculator): See how your own probability assumption changes the result.
- [Kelly calculator](https://getoddsapi.com/kelly-calculator): Explore full and fractional sizing arithmetic.
- [Hedge calculator](https://getoddsapi.com/hedge-calculator): Compare conditional outcomes under entered prices.
- [Arbitrage calculator](https://getoddsapi.com/arbitrage-calculator): Allocate a hypothetical total stake across matching outcomes.
- [Closing-line value calculator](https://getoddsapi.com/closing-line-value-calculator): Compare two supplied prices without claiming a verified close.

## Keep learning or start building

All of these calculators run with user-supplied values. They do not automatically pull live prices or recommend selections. Use the glossary when a term is unclear, and the developer guides when you want to connect an actual documented data source.

Only participate where lawful and within limits you can afford. A formula does not remove the possibility of loss or change the rules of the underlying market.

- [All free calculators](https://getoddsapi.com/tools): Browse the complete set of 15 tools.
- [Betting glossary](https://getoddsapi.com/glossary): Definitions, formulas and worked arithmetic.
- [Developer guides](https://getoddsapi.com/guides): Move from arithmetic examples to source-aware applications.

## Questions

### Do I need an account to use the calculators?

No. The free calculators run in your browser with your inputs. API access is a separate authenticated product.

### Are calculator outputs predictions?

No. Payouts are conditional on the stated outcome, and probability-based calculations depend on the assumptions you supply.

### Can I use the same arithmetic for every market?

Only when the market and settlement assumptions match. Correlation, pushes, voids, deductions and stake-return rules can change the calculation.

## Sources

- [Calculator formulas and assumptions](https://getoddsapi.com/tools)
- [Glossary](https://getoddsapi.com/glossary)
- [Responsible gambling resources](https://www.ncpgambling.org/)

Independent product; not affiliated with the operators named. No picks or predicted profits.

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GetOdds is an independent developer product and is not affiliated with any sportsbook or pick’em operator. Prices describe data, not betting advice.