A simple perl script calling a stastistic module can do that.

# something like this can also do it.

#!/usr/bin/perl

while(){

if (/>/){

$i++;

}else{

chomp;

$seq .= $_;

}

}

$lg = length $seq;

$av = $lg/$i;

print "$av\n";

That is exactly what I needed. Thank you!

You're wellcome

Here are two alternatives for non Perl/Python gurus. They only work if you have a small number of sequences, though.

1, a word/letter count in MS Word, or

2. BLASTing the sequence will also tell you how long it is.

But Pedro gave you a much more elegant solution!