What percentage do normal kidneys function at?

The normal glomerular filtration rate (GFR) for adults is between 90 and 120 milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73 m2). This means that normal kidneys function at a rate of 90-120 milliliters per minute for every 1.73 square meters of body surface area.