Sportsbook odds vs prediction market odds for the same event

Prediction Market Odds Converter

Convert between prediction market % and betting odds

Prediction Market Odds Converter — Polymarket to American/Decimal Odds

Prediction markets like Polymarket, Kalshi, and PredictIt show odds as percentages (e.g. 65% Yes). Traditional sportsbooks use American (-186), Decimal (1.54), or Fractional (7/13) odds. This converter gives you instant bidirectional conversion between all formats so you can compare prediction market prices to sportsbook odds, understand implied probability, and find value. Use it when you see a Kalshi percentage and want to know the equivalent American or decimal odds, or when you have sportsbook odds and want to see the prediction-market-style probability. Use the Prediction Market Odds Converter to get a clear result you can act on right away. This calculator is designed to be practical, fast, and easy to use on any device.

Yes probability (%)

No: 52.4% (auto-calculated)

Results

American

Yes +110 No -110

Yes: bet $100 to win $110. No: bet $110 to win $100.

Decimal

Yes 2.10 No 1.91

Yes: $100 → $210 return. No: $100 → $191 return.

Fractional

Yes 131/119 No 119/131

Profit per unit: Yes 131/119, No 119/131.

Implied prob

Yes 47.6% No 52.4%

Total 100% (no vig)

Market efficiency (vig)

Enter Yes and No prices from a market (e.g. 65¢ Yes, 37¢ No). If they sum to more than 100%, the difference is the vig.

Yes (%)

No (%)

Total: 100.0%

Market vig/margin: 0.0%

Probability to odds reference (1–99%)

Yes-side odds for each whole-number probability. 0% and 100% have no finite odds.

Probability	American	Decimal	Fractional	Profit Per $100
1%	+9900	100.00	99/1	$9900
2%	+4900	50.00	49/1	$4900
3%	+3233	33.33	97/3	$3233
4%	+2400	25.00	24/1	$2400
5%	+1900	20.00	19/1	$1900
6%	+1567	16.67	47/3	$1567
7%	+1329	14.29	93/7	$1329
8%	+1150	12.50	23/2	$1150
9%	+1011	11.11	91/9	$1011
10%	+900	10.00	9/1	$900
11%	+809	9.09	89/11	$809
12%	+733	8.33	22/3	$733
13%	+669	7.69	87/13	$669
14%	+614	7.14	43/7	$614
15%	+567	6.67	17/3	$567
16%	+525	6.25	21/4	$525
17%	+488	5.88	83/17	$488
18%	+456	5.56	41/9	$456
19%	+426	5.26	81/19	$426
20%	+400	5.00	4/1	$400
21%	+376	4.76	79/21	$376
22%	+355	4.55	39/11	$355
23%	+335	4.35	77/23	$335
24%	+317	4.17	19/6	$317
25%	+300	4.00	3/1	$300
26%	+285	3.85	37/13	$285
27%	+270	3.70	73/27	$270
28%	+257	3.57	18/7	$257
29%	+245	3.45	71/29	$245
30%	+233	3.33	7/3	$233
31%	+223	3.23	69/31	$223
32%	+212	3.13	17/8	$213
33%	+203	3.03	67/33	$203
34%	+194	2.94	33/17	$194
35%	+186	2.86	13/7	$186
36%	+178	2.78	16/9	$178
37%	+170	2.70	63/37	$170
38%	+163	2.63	31/19	$163
39%	+156	2.56	61/39	$156
40%	+150	2.50	3/2	$150
41%	+144	2.44	59/41	$144
42%	+138	2.38	29/21	$138
43%	+133	2.33	57/43	$133
44%	+127	2.27	14/11	$127
45%	+122	2.22	11/9	$122
46%	+117	2.17	27/23	$117
47%	+113	2.13	53/47	$113
48%	+108	2.08	13/12	$108
49%	+104	2.04	51/49	$104
50%	-100	2.00	1/1	$100
51%	-104	1.96	49/51	$96
52%	-108	1.92	12/13	$92
53%	-113	1.89	47/53	$89
54%	-117	1.85	23/27	$85
55%	-122	1.82	9/11	$82
56%	-127	1.79	11/14	$79
57%	-133	1.75	43/57	$75
58%	-138	1.72	21/29	$72
59%	-144	1.69	41/59	$69
60%	-150	1.67	2/3	$67
61%	-156	1.64	39/61	$64
62%	-163	1.61	19/31	$61
63%	-170	1.59	37/63	$59
64%	-178	1.56	9/16	$56
65%	-186	1.54	7/13	$54
66%	-194	1.52	17/33	$52
67%	-203	1.49	33/67	$49
68%	-213	1.47	8/17	$47
69%	-223	1.45	31/69	$45
70%	-233	1.43	3/7	$43
71%	-245	1.41	29/71	$41
72%	-257	1.39	7/18	$39
73%	-270	1.37	27/73	$37
74%	-285	1.35	13/37	$35
75%	-300	1.33	1/3	$33
76%	-317	1.32	6/19	$32
77%	-335	1.30	23/77	$30
78%	-355	1.28	11/39	$28
79%	-376	1.27	21/79	$27
80%	-400	1.25	1/4	$25
81%	-426	1.23	19/81	$23
82%	-456	1.22	9/41	$22
83%	-488	1.20	17/83	$20
84%	-525	1.19	4/21	$19
85%	-567	1.18	3/17	$18
86%	-614	1.16	7/43	$16
87%	-669	1.15	13/87	$15
88%	-733	1.14	3/22	$14
89%	-809	1.12	11/89	$12
90%	-900	1.11	1/9	$11
91%	-1011	1.10	9/91	$10
92%	-1150	1.09	2/23	$9
93%	-1329	1.08	7/93	$8
94%	-1567	1.06	3/47	$6
95%	-1900	1.05	1/19	$5
96%	-2400	1.04	1/24	$4
97%	-3233	1.03	3/97	$3
98%	-4900	1.02	1/49	$2
99%	-9900	1.01	1/99	$1

The Formula

Decimal odds = 1 ÷ probability American (favorite, prob ≥ 50%): -(prob ÷ (1 - prob)) × 100 American (underdog, prob < 50%): ((1 - prob) ÷ prob) × 100 Fractional: profit per unit = (1 ÷ prob) - 1, then simplify to a fraction Probability from decimal: prob = 1 ÷ decimal odds Probability from American (negative): prob = (-american) ÷ (-american + 100) Probability from American (positive): prob = 100 ÷ (american + 100) Probability from fractional: prob = denominator ÷ (numerator + denominator) Profit on $100 bet = 100 × (decimal odds - 1)

Examples

65% on Polymarket (Yes)

American Yes: -186, No: +143. Decimal Yes: 1.54, No: 2.86. Fractional Yes: 7/13, No: 13/7.

American -186

Prediction market: 65% Yes / 35% No. Decimal 1.54 (Yes).

Decimal 1.54

Implied probability 64.94%. American -186 (Yes), +143 (No).

💡 Tips

•Use prediction market % as your source of truth when comparing to sportsbooks.
•Lower vig (1–3%) on prediction markets often means fairer prices than sportsbooks.
•Convert both sides (Yes/No) to see full odds in every format.

🎉 Fun Facts

•Prediction markets often show a single percentage (e.g. 65% Yes); the No side is always 100% minus that, with no built-in vig in the display.
•Polymarket and Kalshi use contract prices in cents: 65¢ = 65% probability, so the math is the same as percentage.
•American odds -186 means "bet $186 to win $100" on the favorite; the same 65% probability on the underdog is +143, "bet $100 to win $143".
•Decimal odds (e.g. 1.54) include your stake in the return: a $100 bet returns $154 total (profit $54).
•Fractional odds 7/13 mean you profit £7 for every £13 wagered (UK style); 13/7 is the underdog side for the same market.