How to caculate the needed capacity of the SD card

[mz8e08]

Hi, I gonna interface a microcontroller with SD flash memory card for data log. How to caculate the needed memory capacity?

Thanks

Added after 1 hours 59 minutes:

I've plan to choose a SD card, and thought the bigger capacity the better. But, will it happen that some of the memory addresses can not be accessed? I chosed the msp430F2274 microcontroller.

 

[embeddedlover]

The following steps i have taken,

1.We are going to write to a sector record by record
2.First of all u have to know the max record size.
3.If for example, each record has 100 bytes and u want to write 100 records
then 100 x 100 bytes is your required size.