Expected Value Calculator

Calculate expected value for any sports bet or prediction market position. Supports American odds, decimal odds, implied probability, and Kalshi contract prices. Use when asked about expected value, EV, whether a bet is worth it, +EV opportunities, or breakeven probability.

Calculate the expected value of any bet given offered odds and your estimated true probability.

When to Use

Use this skill when the user asks about:

• Expected value of a bet
• Whether a bet is +EV or -EV
• Is this bet worth taking at these odds
• Breakeven probability for given odds
• Comparing EV across multiple bets
• Finding the best value bets on a slate
• How much edge they have on a line

Odds Conversion Reference

Before computing EV, convert all inputs to decimal odds:

Format	Example	To Decimal Odds
American (+)	+150	1 + odds/100 = 2.50
American (-)	-200	1 + 100/
Decimal	2.50	Already decimal
Implied Prob	40%	1/prob = 2.50
Kalshi price	$0.40	1/price = 2.50

Operations

1. Single Bet EV

Calculate expected value for one bet. User must provide: odds (any format) and their estimated true probability.

python3 -c "
import sys

odds_input = sys.argv[1]
true_prob = float(sys.argv[2]) / 100 if float(sys.argv[2]) > 1 else float(sys.argv[2])

# Convert to decimal odds
if odds_input.startswith('+'):
    decimal_odds = 1 + int(odds_input) / 100
elif odds_input.startswith('-'):
    decimal_odds = 1 + 100 / abs(int(odds_input))
elif odds_input.startswith('$') or odds_input.startswith('0.'):
    price = float(odds_input.replace('$', ''))
    decimal_odds = 1 / price
else:
    decimal_odds = float(odds_input)

implied_prob = 1 / decimal_odds
ev_per_dollar = true_prob * decimal_odds - 1
edge = true_prob - implied_prob

print(f'Offered odds: {odds_input} (decimal {decimal_odds:.3f})')
print(f'Implied probability: {implied_prob:.1%}')
print(f'Your true probability: {true_prob:.1%}')
print(f'Edge: {edge:+.1%}')
print(f'EV per \$1: {ev_per_dollar:+.4f}')
print(f'EV per \$100: {ev_per_dollar * 100:+.2f}')
print(f'Verdict: {\"✅ +EV — BET\" if ev_per_dollar > 0 else \"❌ -EV — PASS\"} ')
" "ODDS" "TRUE_PROB_PERCENT"

## About

Built by [AgentBets](https://agentbets.ai) — full tutorial at [agentbets.ai/guides/openclaw-ev-calculator-skill/](https://agentbets.ai/guides/openclaw-ev-calculator-skill/).

Part of the [OpenClaw Skills series](https://agentbets.ai/guides/#openclaw-skills) for the [Agent Betting Stack](https://agentbets.ai/guides/agent-betting-stack/).