Algorithmic traders use their advantage of speed to execute a large number of small-sized trades in a very short time. In the presence of a minimum trading unit (MTU) restriction, they are forced to trade at the smallest possible sizes, often restricted by the MTU. Using a novel data set of single stock futures market obtained from the National Stock Exchange of India, we show that the MTU restriction acts as a binding constraint for traders while optimizing trade sizes. Contrary to expectation, we find weak evidence that liquidity is positively impacted by the contract size revision.algorithmic trading, contract size, liquidity, minimum trading unit, trading volume Exchange Board of India (SEBI) in 2015, to observe how market participants react to such exogenous shocks. With the introduction of dematerialized trading in the equity market (1999), most of the trading in the Indian equity market at present is carried out in the paperless format with no concept of trading lots or MTU. Traders can buy or sell single units of equity shares. In the derivatives segment, however, the concept of trading in lots is still in vogue where the lot sizes are specific to the underlying security. Unlike most other markets in the world where the MTU is fixed (usually 100 units), in the Indian market, the minimum size of the derivatives contracts is specified by the exchange based on the price level of the underlying stock. During 2015, the market regulator revised the minimum size of a derivative contract upward from INR 0.2 million to 0.5 million. This natural laboratory setup also provides us a unique opportunity to observe the impact of market-wide upward revision of MTU on market liquidity and trading volume.With the introduction of algorithmic trading in various exchanges, presently a significant proportion of trades are initiated automatically from computer terminals without any real-time manual intervention. This paradigm shift in trading mechanism has led traders to adopt appropriate trading strategies to minimize impact costs. Over the last decade and a half, the average trade size in exchanges over the globe has significantly reduced 2 (Angel, Harris, & Spatt, 2011;O'Hara, Yao, & Ye, 2014), owing much of it to the increase in algorithmic trading activity. Aitken, Cumming, and Zhan (2017) show that the introduction of algorithmic trading and high-frequency trading (HFT), proxied by colocation services, significantly impacts trade sizes. Traders often face a challenge of choosing optimum trade sizes to reduce overall impact cost and transaction cost (Bertsimas & Lo, 1998), especially when confronted with the problem of buying or selling a predefined quantity. Algorithmic traders use their advantage of speed to split a larger order into smaller lots so that the price impact is minimal. They are more likely to carry out a large number of small trades throughout the day rather than a few bulk trades. Algorithmic traders are also mostly intraday traders who rarely carry over their positions to the next trading day. 3 In this c...