Here, we will write the binary number that we want to convert.
For example, let us use a binary number 1101101.
Here, we will start from the rightmost bit (least significant bit) and raise each bit to the power of 2 moving from right to left. The rightmost bit is 2^0, the next is 2^1, then 2^2, and so on.
Our example using 1101101
2^6   2^5   2^4   2^3   2^2   2^1   2^0
—————————————-
1        1        0       1       1       0       1
We will multiply each bit by its corresponding power of 2 and sum the results.
Using the example 1101101 –
(1 * 2^6) + (1 * 2^5) + (0 * 2^4) + (1 * 2^3) + (1 * 2^2) + (0 * 2^1) + (1 * 2^0)
= 64 + 32 + 0 + 8 + 4 + 0 + 1
= 109
Therefore, the binary number 1101101 is equivalent to the decimal number 109.