Your fingernails grow nearly four times faster than your toenails.

Scientists like Dr. William Bean have studied nail growth for decades to understand these differences. On average, a fingernail grows about 3.5 millimeters every month, while a toenail only manages about 1.6 millimeters. This means it takes about 6 months to grow a whole new fingernail, but it can take up to 18 months for a toenail to fully replace itself.The main reason for this speed is blood flow. Your hands have a very thick network of tiny blood vessels called capillaries. These vessels carry oxygen and food to the nail matrix, which is the 'factory' under your skin where new nail cells are made. Because your hands are closer to your heart than your feet, the blood reaches them with more pressure and volume.Even the specific finger matters. Research shows that your middle fingernail usually grows the fastest, while your thumbnail and pinky nail grow a bit slower. This might be because longer fingers have more blood vessels or because we use them more. Using your hands for things like typing or playing sports creates tiny vibrations that stimulate growth.Weather and age change things too. Nails grow faster in the summer because the sun helps your body make Vitamin D and the warmth improves circulation. As you get older, the process slows down. After you turn 25, your nail growth drops by about 0.5% every single year.