Each retina has a place where the optic nerve leaves the eye. All the nerve fibres from the retina gather there and exit through a small round area called the optic disc. That area has no rods or cones, so light that lands on it is not detected. This is your blind spot (the medical name is the physiological scotoma).

The optic disc sits about 15 degrees away from the centre of your gaze, on the side towards your ear (the temporal side). Its width is roughly 5 to 7 degrees of visual angle. That is large: roughly ten full Moons side by side (the Moon is about half a degree wide) could disappear in it.