How do astronauts weigh themselves in space? 

 In microgravity, astronauts must measure their mass, not their weight, which they can do with two devices on the ISS. 

https://cdn.mos.cms.futurecdn.net/KirbD9zqdtzxQzXtpXf8qV.jpg

https://www.space.com/space-exploration/human-spaceflight/how-do-astronauts-weigh-themselves-in-space