Arbitrage Betting Calculator: Kalshi & 3-Way Stake Sizing (2026)
Free Kalshi arbitrage calculator and 3-way arbitrage calculator. Size Polymarket–Kalshi legs, sportsbook surebets, and three-outcome arbs with fee-adjusted profit.
Last updated: August 2026 — Use the interactive tool at /arbitrage-calculator. Pair it with our arbitrage bet finder guide to discover opportunities first.
What is a Kalshi arbitrage calculator?
A Kalshi arbitrage calculator sizes YES/NO legs when Kalshi and another platform (usually Polymarket) price the same event differently. Enter contract prices in cents, your total budget, and optional Kalshi fees — the calculator returns per-leg stakes and net ROI.
- Binary contracts — each side pays $1.00 at settlement; combined cost below $1.00 means risk-free profit
- Fee-aware — Kalshi's ~7% taker fee on the relevant leg reduces net spread
- Works with live prices — paste asks from the free arbitrage finder or Polymarket–Kalshi scanner
Try it now: Kalshi arbitrage calculator (prediction-market mode).
What is a 3-way arbitrage calculator?
A 3-way arbitrage calculator handles events with three outcomes — common in soccer (home / draw / away). When three sportsbooks offer odds where implied probabilities sum to less than 100%, you can stake across all three and lock profit regardless of result.
- Three decimal or American odds — input best price per outcome from different books
- Optimal stake split — proportional to inverse implied probability
- ROI check — negative ROI means no arb exists after rounding
Try it now: 3-way arbitrage calculator (3-way mode).
Kalshi arbitrage calculator — worked example
| Leg | Platform | Side | Price | Action |
|---|---|---|---|---|
| 1 | Kalshi | YES | 58¢ | Buy |
| 2 | Polymarket | NO | 35¢ | Buy |
- Total cost: 93¢ per contract pair
- Guaranteed payout: $1.00
- Gross profit: 7¢ (~7.5% ROI before Kalshi fees)
- On $500 budget: calculator returns exact contract count and per-platform dollar amounts
After Kalshi fees, net ROI is often 5–6% — still profitable if you execute both legs quickly. Scan live pairs with the prediction market arbitrage finder.
3-way arbitrage calculator — worked example
Three outcomes from different books:
| Outcome | Book | Decimal odds | Implied prob |
|---|---|---|---|
| Team A wins | Book 1 | 2.10 | 47.6% |
| Draw | Book 2 | 3.60 | 27.8% |
| Team B wins | Book 3 | 4.00 | 25.0% |
- Sum of implied probs: 100.4% — no arb (overround)
- If sum were 97%, a 3% arb exists; the calculator splits a $300 stake into ~$154 / $89 / $57 across the three legs
Use the arbitrage calculator 3-way tab instead of guessing stakes by hand.
Calculator vs finder vs API
| Tool | Purpose | Link |
|---|---|---|
| Arbitrage bet finder | Discover live mispricings | Guide · Scanner |
| Arbitrage calculator | Size stakes for a known arb | /arbitrage-calculator |
| Arbitrage betting API | Automate discovery + sizing in code | /arbitrage-api · Docs |
Best practices
- Always net out fees — a 2% gross Kalshi spread can be zero after taker fees
- Check orderbook depth — top-of-book prices may not fill your full size
- Act fast — run the calculator before placing orders; spreads close in minutes during volatile events
- Pair with education — read how arbitrage bet finders work and the prediction markets arbitrage guide
Related resources
- Arbitrage betting explained — surebet fundamentals
- Value betting finder — +EV plays when pure arbs are scarce
- Arbitrage betting API — programmatic access for bots
- Pricing — Pro scanner and Premium API plans
Conclusion
A Kalshi arbitrage calculator and 3-way arbitrage calculator remove guesswork from stake sizing. Use the interactive calculator for instant results, the arbitrage bet finder to discover opportunities, and the API docs if you are building automated workflows.