# How to check if a thing I have is exactly of 1 kg or not?

The definition of a kilogram is as far I know,

Kilogram: The mass of a cylinder made of platinum-iridium alloy kept at International Bureau of Weights and Measures is defined as 1 kg.

But it is not possible to go and check that reference all the time. So is there any way to check the accuracy of checking 1kg?

• You can be sure you'll never have exactly 1kg with infinite precision. The thing is: what precisioni is enough for you? Then you'll have to look for an appropiate instrument, and you have to rely on the technical specification and the calibration certificate. May 22, 2018 at 20:30
• I am not asking about much precision. Lets assume It will be ok if I can check if my daily needs bread, flour are exact 1 kg or 999 gm. May 22, 2018 at 20:43
• You're missing FGSUZ's point. If you use a kitchen scale to weigh out 1kg of flour, and the readout on the scale says "1000 g", that does not mean that you have exactly 1kg of flour on the scale. Even if your scale was perfectly accurate, it still would only mean that you had somewhere between 999.5 g and 1000.5 g. May 22, 2018 at 21:52
• May 22, 2018 at 21:56
• Yes that is what i am confused about, how do i know had somewhere between 999.5 g and 1000.5 g. it may be < 999.5 , the weight on amazon, how can i trust that also May 23, 2018 at 5:42