I recalibrated the bathroom scale to keep the wife happy, so I can't weigh my planes accurately with it.

Seriously, I use a 15lbs digital fish scale for weighing planes and a 5lbs postal scale for weighing engines. Try to pick a scale where you're staying between 1/4 and 4/5 full scale. Too light and it won't be accurate; too heavy and you're liable to damage the strain gauge inside (if it uses one).