How Share Prices Are Determined: Order Matching, Demand and Supply and What Really Moves a Stock

A share price is the last price at which a buyer and a seller agreed to trade. The exchange matches the highest bid with the lowest ask, giving priority to price first and then time.

How share prices are determined is a question every investor asks once they see a stock rise or fall for no obvious reason. The honest answer is that a price is not a verdict on a company. It is simply the latest agreement between one buyer and one seller.

This guide walks through the order matching process, the role of demand and supply, the factors that shift both, and why the price you see can differ from the value you calculate.

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How Share Prices Are Determined on the Exchange

Every buyer and seller sends orders to the exchange. Buy orders are called bids, and sell orders are called asks. The exchange’s matching engine pairs the highest bid with the lowest ask. When they meet, a trade happens, and the price of that trade becomes the last traded price.

This process is called price discovery. It runs continuously through the trading session, which is why a price changes many times in a minute for an active stock.

Order Matching: Price-Time Priority

Orders are matched by price first and then by time. A buyer offering a higher price is served before a lower bid, and among orders at the same price, the earlier one is served first. That rule rewards both aggressive pricing and early placement.

Before the continuous session begins, a pre-open call auction collects orders and finds the single price at which the most shares can trade. That price becomes the opening price for the day.

Liquidity matters too, because a stock with many active buyers and sellers sees smaller price jumps on each trade.

Demand and Supply: The Engine Behind Price Moves

If more people want to buy than sell at the current price, buyers must offer higher prices to attract sellers, and the price rises. If more people want to sell, sellers must accept lower prices, and the price falls. Almost every factor that moves a stock works by shifting this balance.

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What Changes Demand and Supply for a Stock?

Why a Share Price Is Not the Same as Value

A price of Rs 500 does not mean a company costs less or more than one trading at Rs 5,000. The number of shares, earnings and growth differ for each company, so only measures such as market capitalisation and valuation ratios allow fair comparisons. Prices can also stay above or below value for long periods because sentiment is not always rational.

How a Single Stock Relates to the Index

An index such as the Nifty 50 is a weighted average of the prices of its constituent companies. A stock can fall on a day when the index rises, because its own demand and supply were different from the market’s. Daily circuit limits also cap how far a single stock can move in a session.

For a long-term investor, the useful lesson is that short-term price moves tell you about the mood of the market, while business results tell you about the company.

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Conclusion

How share prices are determined is a continuous contest between buyers and sellers, settled by the exchange’s matching engine on a price-time priority basis. Demand and supply carry the effect of earnings, news, rates, flows and sentiment into the price.

Treat the price as the market’s current opinion, not as a fixed measure of worth, and compare companies using valuation, not just the rupee price.

Frequently Asked Questions

How are share prices determined in India?

Ans. Share prices are determined by the exchanges, where buy and sell orders are matched continuously. The highest bid is paired with the lowest ask, and the price of the latest trade becomes the market price. Demand and supply drive the orders.

Who decides the price of a share?

Ans. No single person decides it. The price emerges from the combined orders of all buyers and sellers. A company can influence perception through results and announcements, but the price itself is set by the order book on the exchange.

What is price discovery?

Ans. Price discovery is the process by which the market finds the price at which buyers and sellers agree to trade. It happens through order matching during the session and through the pre-open call auction that sets the opening price.

Why do share prices change every second?

Ans. New orders arrive and old ones are cancelled all the time. Each time a bid meets an ask, a trade occurs at a new price. For active stocks, this happens many times a minute, so the last traded price keeps updating.

Does a high share price mean a company is expensive?

Ans. Not necessarily. The rupee price on its own says little, because companies have different numbers of shares. To judge whether a company is expensive, compare valuation ratios such as price to earnings with its own history and with peers.

What is price-time priority?

Ans. It is the rule used by the exchange to match orders. Orders with a better price are served first, and among orders at the same price, the one placed earlier is served first. It makes the matching process orderly and transparent.

Can news move a share price immediately?

Ans. Yes. Fresh news changes expectations, and traders adjust their bids and asks within seconds. Prices can jump or fall quickly on results, regulatory decisions or large orders, although daily circuit limits cap the size of a one-day move.