When there's no mode
5, 8, 12, 19, 24 has five values and every one of them appears exactly once — no value repeats more than any other, so there's nothing that qualifies as "the most common value." The mean (13.6) and median (12) both still exist and are meaningful for this list; mode simply doesn't apply here.
When there's more than one mode
1, 2, 2, 3, 3, 4 has two values tied for the highest frequency — both 2 and 3 appear twice, more than 1 or 4 (which appear once each). A list like this is called "multimodal," and the correct answer is to report both tied values (2 and 3) rather than arbitrarily picking one. The mean (2.5) and median (2.5) are unaffected by this tie — they only depend on the values and their positions, not on how many modes exist.
Why this matters when choosing mode over mean or median
Mode is genuinely useful when repeated values are expected and meaningful — survey responses, shoe sizes sold, exam scores rounded to whole numbers. For continuous measurements (heights, prices, durations) where exact repeats are rare or coincidental, "no mode" is a common and largely uninformative result — a sign that mean or median is probably the more useful summary for that kind of data, not that something went wrong with the calculation. See the companion article on choosing between mean, median, and mode for the fuller picture of when each one is the right tool.
What the calculator shows
When every value is unique, the mode result reads "No mode" rather than guessing at one. When two or more values are tied, all of the tied values are listed together — so a result like "2, 3" means both of those values are genuinely tied for the highest frequency, not that something is ambiguous about the calculation.