When you flip a coin, there are two possible outcomes: heads or tails. The probability of getting heads or tails can be calculated as follows:
\[ P(\text{heads or tails}) = P(\text{heads}) + P(\text{tails}) = \frac{1}{2} + \frac{1}{2} = 1 \]
Thus, \( P(\text{heads or tails}) \) is \( 1 \), which means it is certain that you will get either heads or tails.
The simplified answer is:
\[ \boxed{1} \]