Calculation of Power Dissipation of Memory ICs and Microcontrollers
This is always something of an estimate and I am usually interested in average power.

For a memory device you need to know:

1 The amount of time you will be writing to the device as a fraction of total time (if at all but remember that you must consider the minimum time the device will be writing on each occasion).

2 The amount of time you will be reading from the device as a fraction of total time.

(The interface speed may matter for capacitive power dissipation).

Here I am assuming a single power rail (fairly typical for most memory devices).

Find the write current from the datasheet and multiply it by the device voltage and then multiply by the fraction of total time you are writing. If you are writing for 5% of the time, the write current is 20mA and the voltage is 3.3V, then you have an average write power of 3.3mW. (The peak power here is 66mW)

If you are reading for 70% of the time, find the read current and multiply it by the device voltage and then by the fraction of time you are reading; for a read current of 15mA and a device voltage of 3.3V, then the average read power is 34.65mW.

Now just add the two together for total average active power (37.95mW in this case). Now add this to the standby power multiplied by the time the device is inactive as a fraction (1 - write time - read time) and you have the answer (as an estimate - I usually add 10% to this as a margin).

This does not take into account a long sequence of writes which may cause localised self heating for a short period of time.