When two black holes merge, they form a bigger black hole. This bigger black hole will have around 95% of the mass of its two parent black holes. The remaining 5% is carried away as the energy in the gravitational waves
We measure black hole masses in solar masses (our Sun is 1 solar mass)
The biggest black holes we have seen are the merger remnants for
⚫️GW200220_061928 around 140 solar masses
⚫️GW190521 around 150 solar masses
⚫️GW190426_190642 around 170 solar masses
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