In standard use your code goes into the 8 Kbytes of Flash memory and variables go into the 1 Kbyte of SRAM. Note that because a hex file represents a single byte as a pair of hexadecimal characters and contains some other information it will be over twice the size of the actual code that will be loaded, so a hex file a bit over 16K should load.

The most reliable place to find out of much Flash and SRAM your code uses is from the compiler. If you're using Atmel Studio 6 in the build output area if you scroll up you should see something like:

Program Memory Usage : 540 bytes 0.8 % Full

 

Data Memory Usage : 0 bytes 0.0 % Full

So the program memory use shows how much of the Flash will be used and data memory usage shows how much of the SRAM will be used.

In standard use your code goes into the 8 Kbytes of Flash memory and variables go into the 1 Kbyte of SRAM. Note that because a hex file represents a single byte as a pair of hexadecimal characters and contains some other information it will be over twice the size of the actual code that will be loaded, so a hex file a bit over 16K should load.

The most reliable place to find out of much Flash and SRAM your code uses is from the compiler. If you're using Atmel Studio 6 in the build output area if you scroll up you should see something like:

Program Memory Usage : 540 bytes 0.8 % Full

Data Memory Usage : 0 bytes 0.0 % Full

So the program memory use shows how much of the Flash will be used and data memory usage shows how much of the SRAM will be used.