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Stumped - Online conversions don't match 2 precision scales

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  • Stumped - Online conversions don't match 2 precision scales

    I have a precision lab scale. After calibration and tare, an item weighs .1023 ounces. Switching to grams, tare the scale, and it weighs 3.184 grams. Verifying with 6 different online weight conversions all show that the oz weight would be 2.900 grams, not 3.184 grams. First thinking is that the scale is the issue so I get out my jeweler's scale. I weigh the same item 4 times on each scale for ounce and gram weight. All weights are nearly exact. After 4 different weights on both scales the weight of the item is between .1022-.1024 oz. Switch to grams and repeat. Both scales weigh out between 3.183-3.185 grams.

    Here is the confusion. Checking multiple online weight conversions show that the weight of .1023 ounces will be 2.9002 grams. It does not make sense. What am I missing here?


  • #2
    Your scale is using Troy ounces.

    0.1022 troy ounces = 3.179 grams


    • #3
      In Customary or Imperial, precious metals are weighed in troy ounces, not avoirdupois ounces. The troy ounce is 31.1034768 grams, while the avoirdupois ounce (used to weigh everything else) is 28.349523125 grams. See Wikipedia article on "ounce" for the multiple meanings of the word. There are also fluid ounces and they differ between Imperial and Customary.