A 95-percent illuminated moon is half as bright as a full moon

Most observers probably can’t tell the difference between the Moon when 95% of it is lit up and when its 100% visible, but there’s a sizeable difference - 0.7 magnitudes. The apparent magnitude of any celestial body is a measure of how bright it appears to be from Earth - the brighter an object is, the lower its magnitude. Remarkably, just 2.4 days before and after a full moon, the Moon appears 50% dimmer!