I am going to suggest doing what PaulS recommended. This works on my Mega2560.
// include the freeRam function in your sketch
int freeRam() {
extern int __heap_start,*__brkval;
int v;
return (int)&v - (__brkval == 0 ? (int)&__heap_start : (int) __brkval);
}
void setup() {
Serial.begin(9600);
// then use it like this
Serial.print("SRAM free: ");
Serial.println(freeRam());
}
void loop() {
}