You’ve successfully tested the limits of how much can fit into a #10 envelope without bursting its seams, but now you’re questioning how much postage you need. Sure you could just slap a few of the new 44-cent stamps onto whatever you're sending and be done with it, but that’s good money you’re throwing away.
Instead, spend just a few bucks now to build a simple magnetic postage scale, newly updated from an original article in the February 1971 issue of Popular Science.
This handy little device works by balancing the unknown weight (your obese letter) against a calibrated opposing force developed by five or six small ring magnets poled to repel each other.
Go ahead and make your own!
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Inside NASA's astronaut bootcamp and the grueling new training regimen for deep space. Plus, ten young geniuses shaking up science today, one writer's quest to analyze every man-made chemical in her body and more.
Check out the issue's full contents online here





It's important to remember that pennies pre 1982 were 3.1 grams, but pennies after 1982 are 2.5 grams. You should adjust for calibration accordingly. Also 28.34 grams is an ounce (avoirdupois) these days.