Order book simulator
Place an order into a live order book and watch it fill, so you understand the difference between the price you saw and the price you got.
Runs entirely in your browser — nothing you type is sent anywhere. Educational only, and not investment advice.
How to use this calculator
Each step names a control you will find on screen above.
- Side
Buy or sell. Note that a buy fills against the ask side and a sell fills against the bid — you always trade against the opposite queue.
- Order type
Market takes whatever price is available right now. Limit specifies your worst acceptable price and waits. Everything else follows from that one distinction.
- Quantity
Increase it and watch a market order eat through several price levels. This is slippage, and it is why a large order in a thin stock costs more than the screen suggests.
- Your limit price
Set it away from the market and the order joins the queue instead of filling. Certainty of price and certainty of execution are a genuine trade-off.
Worked example: A market order that walks the book
The best offer is 200 shares at ₹500.05, then 300 at ₹500.20, then 1,000 at ₹500.60. You send a market buy for 1,000 shares.
What to enter
- Side
- Buy
- Order type
- Market
- Quantity
- 1,000
What it shows you
- First 200
- ₹500.05
- Next 300
- ₹500.20
- Final 500
- ₹500.60
- Average fill
- ≈ ₹500.35
- Cost of slippage
- ≈ ₹300
against the ₹500.05 you saw
Where this is taught
A calculator gives you a number. These explain what the number means and when it misleads you.
- Market Basics11 minHow a price is actually formedTick sizes, the pre-open auction, algorithms, block deals and circuit filters — the machinery beneath the number on your screen.
- Technical Analysis10 minOrder flow and reading the tapeWhat the depth book and the trade tape actually show, what can be inferred from them, and an honest account of the limits for a retail trader.
- Market Basics11 minOrder types, and the order book behind themMarket, limit, stop-loss and GTT — what each one actually does to the order book, and why choosing wrong is expensive.
- Market Basics10 minReading a stock quote screenLTP, OHLC, market depth, delivery percentage, circuit limits and the 52-week range — every number on the screen and which ones actually matter.
- Technical Analysis12 minGetting the order you actually intendedGTT, AMO, stop-loss market versus limit, iceberg and bracket orders. The mechanics that decide whether your plan survives contact with the order book.