Open any Google Scholar profile and you'll see two numbers sitting side by side: h-index and i10-index. They're often mentioned in the same breath, which leads a lot of researchers to assume they're roughly interchangeable. They're not — they're built on different logic, and understanding that difference matters more than it looks.
What Each One Actually Counts
The i10-index is the simpler of the two: it is just the number of papers that have received at least 10 citations. A researcher with 40 papers, 12 of which have 10 or more citations each, has an i10-index of 12. That's the entire calculation — no sorting, no threshold curve, just a straightforward count against a fixed bar.
The h-index is more involved. A researcher has an h-index of h if h papers have each been cited at least h times, and the rest have fewer citations than that. Unlike the i10-index's fixed threshold of 10, the h-index's threshold moves with the researcher's own output — it's a self-referential balance between how many papers you've published and how well each one has been cited.
Why the Difference Matters in Practice
Because the i10-index uses a flat threshold, it rewards volume more directly. A researcher who publishes prolifically will see their i10-index climb steadily as more papers cross the 10-citation line, even if none of those papers become field-defining. The h-index resists that kind of inflation — publishing ten more modestly-cited papers won't move your h-index if they don't also clear the rising bar the metric sets.
This is also why the i10-index is far less commonly requested on formal documents. Grant applications, tenure files, and job postings overwhelmingly ask for h-index specifically, because committees have converged on it as the shorthand for "sustained, broadly-recognized impact." The i10-index shows up mostly as a secondary, informal indicator — useful context on a Google Scholar profile, but rarely the number anyone is actually evaluating you against.
A Worked Comparison
Take two researchers with the same total citation count. Researcher A has 20 papers, each cited exactly 10 times — an i10-index of 20 and an h-index of 10 (since only 10 papers can each have at least 10 citations while also occupying positions 1 through 10 in the sorted order... in this even case, all 20 clear 10, but the h-index caps at the point where position number exceeds citations, landing at 10). Researcher B has 5 papers cited 40 times each — an i10-index of 5, but an h-index of 5 as well, since only 5 papers exist to count. Same total citations, very different profiles: the i10-index makes Researcher A look four times more prolific, while the h-index tells a closer, though still distinct, story about each one's depth.
Get Both Numbers in One Step
Since both metrics are calculated from the exact same input — a list of your papers' citation counts — there's no reason to calculate them separately. Know Your Faculty's [free H-Index Calculator](/h-index-calculator) returns your h-index and i10-index side by side the moment you paste in your citation counts, so you can see both figures the way a Google Scholar profile would show them, without needing a Scholar profile at all.