Withdrawable balance is the amount of money you can transfer from the trading account to your bank account. Your withdrawable balance may differ from the total available funds in your account since funds from trades are not immediately settled. 

In India, exchanges follow a rolling settlement cycle. If you sell stocks or make intraday profits, you will be able to utilise the proceeds to buy other shares. However, funds from the sale proceeds get settled to your trading account after two trading days. Similarly, trades in the F&O segment get settled after one trading day.

You will be able to withdraw only the funds that have been settled to your account. 

The withdrawable balance is calculated in the following way:

Withdrawable balance = Available Ledger balance minus Proceeds from stocks sold yesterday & today minus Intraday equity profit made yesterday & today minus F&O profits today minus Accrued Interest minus Accrued DP charges minus required Margins (if you have taken any derivative positions) minus exchange accrued penalty minus any other charges as applicable to your account.

You should note the withdrawable balance is computed after adjusting the margins blocked if you've pledged your holdings and raised margins to trade in the derivative segment with available cash balance:

50% of the margins blocked have to come in the form of collateral margins & the other 50% by way of cash or cash equivalent. If you do not have enough collateral margins to cover for 50% of the margin blocked, the difference will be charged from the available cash balance

Here's an example to help you understand better:

Assume, you have collateral margin of Rs 1 Lakh from pledged stocks after the required haircut. You also have Rs 70,000 free cash in your account and then take an overnight F&O position which requires a margin of Rs 1 lac.

In this case, you will be able to utilize up to 50% of the required margin using the pledged stocks i.e. Rs 50,000. The remaining 50,000 margin has to be covered by cash. This leaves you with a withdrawable balance of Rs. 20,000.