{"id":14266,"date":"2026-05-27T07:40:17","date_gmt":"2026-05-27T07:40:17","guid":{"rendered":"https:\/\/lemonn.co.in\/blog\/glossary\/kelly-criterion\/"},"modified":"2026-05-27T07:40:17","modified_gmt":"2026-05-27T07:40:17","slug":"kelly-criterion","status":"publish","type":"glossary","link":"https:\/\/lemonn.co.in\/blog\/glossary\/kelly-criterion\/","title":{"rendered":"Kelly Criterion"},"content":{"rendered":"

The Kelly Criterion<\/a> is a mathematical formula that calculates the optimal fraction of your capital to bet or invest on each trade or bet to maximise the long-term growth of wealth. It tells you exactly how much to risk given your win rate and the ratio of average wins to average losses.<\/p>\n

What Is the Kelly Criterion?<\/h2>\n

The Kelly Criterion was developed by John L. Kelly Jr. in 1956 at Bell Labs. It is used in gambling, investing, and trading<\/a> to determine the optimal bet size.<\/p>\n

**Formula:**
\nKelly % = W – [(1 – W) \/ R]<\/p>\n

Where:
\n– W = win rate (probability of winning)
\n– R = win\/loss ratio (average win \/ average loss)<\/p>\n

**Example:**
\nWin rate (W) = 50%
\nAverage win = Rs 3,000
\nAverage loss = Rs 2,000
\nR = 3,000 \/ 2,000 = 1.5<\/p>\n

Kelly % = 0.50 – [(1 – 0.50) \/ 1.5] = 0.50 – 0.333 = 0.167 = 16.7%<\/p>\n

This means betting 16.7% of your capital on each trade maximises long-term growth.<\/p>\n

Why the Kelly Criterion Matters<\/h2>\n

Betting too little results in slower capital growth. Betting too much (overbetting) leads to greater risk of ruin and lower long-term growth due to the asymmetric effect of losses.<\/p>\n

The Kelly formula balances these two risks to find the mathematically optimal bet size.<\/p>\n

Half-Kelly: The Practical Versi<\/a>on<\/h2>\n

Full Kelly can result in very large drawdowns because real-world win rates and risk-reward ratios are not perfectly consistent. Most professional investors and traders use Half-Kelly (bet half the Kelly fraction) to reduce volatility<\/a> while still compounding at a good rate.<\/p>\n

Half Kelly % = Kelly % \/ 2 = 8.35% in the example above.<\/p>\n

Limitations of Kelly Criterion<\/h2>\n

– Requires accurate estimates of win rate and win\/loss ratio, which are hard to determine in advance
\n– Assumes the same edge is available on every bet\/trade (unrealistic in markets)
\n– Can still result in large drawdowns with full Kelly
\n– Works over very long periods; short-term results can be very volatile<\/p>\n

Practical Example<\/h2>\n

Rohit has backtested his swing trading<\/a> strategy and found a 55% win rate with an average win of Rs 2,400 and average loss of Rs 1,500. R = 2,400\/1,500 = 1.6. Kelly % = 0.55 – (0.45\/1.6) = 0.55 – 0.28 = 0.27 = 27%. He uses Half Kelly of 13.5%, risking Rs 1.35 lakh of his Rs 10 lakh account on each swing trade. This is a well-informed, mathematically derived position sizing<\/a> decision.<\/p>\n

Key Takeaways<\/h2>\n

– The Kelly Criterion calculates the optimal fraction of capital to invest to maximise long-term wealth
\n– Formula: Kelly % = W – [(1-W) \/ R], where W is win rate and R is win\/loss ratio
\n– Most practitioners use Half-Kelly to reduce variance while still growing capital efficiently
\n– Requires accurate estimates of win rate and win\/loss ratio from historical performance
\n– Overbetting (ignoring Kelly) leads to higher ruin risk; underbetting slows down compounding<\/p>\n","protected":false},"excerpt":{"rendered":"

The Kelly Criterion is a mathematical formula that calculates the optimal fraction of your capital to bet or invest on each trade or bet to maximise the long-term growth of wealth. It tells you exactly how much to risk given your win rate and the ratio of average wins to average losses. What Is the […]<\/p>\n","protected":false},"author":3,"featured_media":0,"menu_order":0,"template":"","meta":{"_uag_custom_page_level_css":"","footnotes":""},"class_list":["post-14266","glossary","type-glossary","status-publish","hentry"],"blocksy_meta":[],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false,"web-stories-poster-portrait":false,"web-stories-publisher-logo":false,"web-stories-thumbnail":false},"uagb_author_info":{"display_name":"Team Lemonn","author_link":"https:\/\/lemonn.co.in\/blog\/author\/ashu\/"},"uagb_comment_info":0,"uagb_excerpt":"The Kelly Criterion is a mathematical formula that calculates the optimal fraction of your capital to bet or invest on each trade or bet to maximise the long-term growth of wealth. It tells you exactly how much to risk given your win rate and the ratio of average wins to average losses. What Is the…","_links":{"self":[{"href":"https:\/\/lemonn.co.in\/blog\/wp-json\/wp\/v2\/glossary\/14266","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lemonn.co.in\/blog\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/lemonn.co.in\/blog\/wp-json\/wp\/v2\/types\/glossary"}],"author":[{"embeddable":true,"href":"https:\/\/lemonn.co.in\/blog\/wp-json\/wp\/v2\/users\/3"}],"version-history":[{"count":0,"href":"https:\/\/lemonn.co.in\/blog\/wp-json\/wp\/v2\/glossary\/14266\/revisions"}],"wp:attachment":[{"href":"https:\/\/lemonn.co.in\/blog\/wp-json\/wp\/v2\/media?parent=14266"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}