pg 7.4.2 estimate disk usage

oramind

sorry to type english.

is there a general rule of counting disk space usage?

for example, one table with 3 integer columns, no index.
what's the expected disk usage of 100k rows, 1M rows, 10M rows, etc.

integer is 32 bit, so 4 bytes.  and with some overhead..

but it seems like pg is using more space than i expect.

i have installed oid2name and dbsize.  but don't seem to tell me why it's taking more space.

also, it's brand new inserts.  no updates, no deletes.  so should be nothing really to vacuum.

any suggestions?