Each time a fair coin is tossed, the probability of getting tails (not heads) is 1/2 = 0.5. When three coins are tossed, the probabilities of getting tails on each coin are multiplied. Thus, the probability of no heads is

`1/2 * 1/2 *1/2 = 1/8 = 0.125`

The probability is 1/8, 0.125, or 12.5%.