Work out counting practice instantly with clear inputs, formula shown and shareable results.
Counting inclusively gives high minus low plus one numbers, and their total is the arithmetic-series sum (first + last) x count / 2. The off-by-one in inclusive counting is one of the most common early mistakes, and the series sum gives a self-check that a hand count can be compared against.
Inclusive count
count = end - start + 1
Series sum
sum = (start + end) x count / 2
count = end - start + 1. Counting inclusively gives high minus low plus one numbers, and their total is the arithmetic-series sum (first + last) x count / 2.
The off-by-one in inclusive counting is one of the most common early mistakes, and the series sum gives a self-check that a hand count can be compared against.
Enter count from, count to. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.