How many candidates should you screen?
Reading applications or interviewing a shortlist — same maths, different pool. Pick your step below. To be 90% sure the best one you see is in the top 10%, you need about 20 — whether the pile is 50 or 500.
Which step are you sizing?
Your pool is everyone who applied — not just the ones you have opened. Often a few hundred.
= the best 20 of 200
Review this many
21
of your 200 applications, for a 90% chance the best of them is in the top 10%
- One more review adds
- +1.1%
- Reviewing all 200
- 100%
Reviewing every one would mean 179 extra reviews to buy the last 10% of certainty.
No benchmarks are used here — this is arithmetic over your own numbers. It does assume that the applications you open are a fair sample of the pile, and that reading one tells you who is stronger. The second is the one that bites.
Ten times the pile, four more looks
A flood of applications does not mean a flood of screening. What it actually takes to be confident the best candidate you screened is in the top 10% of the pool:
| Candidates in the pool | Screen this many for 90% confidence | For 95% |
|---|---|---|
| 50 | 18 | 22 |
| 100 | 20 | 25 |
| 200 | 21 | 27 |
| 500 | 22 | 28 |
A ten-fold bigger pile costs four extra looks. What a bigger pool really changes is who is in it to be found — not how deep you have to dig.
How the number is calculated
The whole derivation rests on one observation: "the best of the ones I screened is in the top 10%" is the same statement as "at least one of the ones I screened is in the top 10%". If the group you looked at contains any top-10% candidate, then the best one in that group is at least that good. So the question becomes a straightforward sampling probability:
P = 1 − C(N−m, k) / C(N, k)
- N — how many candidates are in the pool at this stage (everyone who applied, if you are reviewing applications; everyone shortlisted, if you are interviewing).
- m — how many of them clear your bar (the top 10% of a 200-candidate pool is 20 people).
- k — how many of them you actually screen.
Exact, not a simulation. It assumes the screening step ranks correctly what it sees — the optimistic end of the predictor-validity axis that the Taylor-Russell tables (1939) have measured hiring against ever since, and the reason screening more people cannot fix a screen that cannot sort them. It is also not the secretary problem or the "37% rule", which solve a sequential no-recall problem that does not describe batch shortlisting.
Frequently asked questions
Does this mean interviewing candidates or reviewing applications?▾
Either — pick the step in the calculator and it relabels itself. The maths is identical at both, because both are the same act: you look at part of a pool and choose the best of what you saw. What differs is the pool. If you are reviewing applications, the pool is everyone who applied, often a few hundred. If you are interviewing, the pool is your shortlist, usually ten or twenty. Enter the pool for the step you are actually about to do, or the answer will be for a different question.
Why does the interview stage tell me to see almost everyone?▾
Because a shortlist is already the good part of the pool, so the top 10% of it is a far higher bar than the top 10% of all applicants — on a shortlist of twenty, it is two people. Finding one of two among twenty genuinely does mean interviewing most of them. That is not the calculator misfiring; it is the reason skipping people late in a process costs you much more than skipping people early. The place to be selective about your own effort is the application pile, not the shortlist.
How many candidates should you interview before deciding?▾
For a 90% chance that the best person you see is in the top 10% of the pool you are choosing from, you need about 20 — and that barely changes with pool size. It is 18 for a pool of 50 and 22 for a pool of 500. The number depends far more on how good a hire you need than on how many people are in the pool. Note that at the interview stage the pool is your shortlist, not your total applicant count.
Does a bigger applicant pool mean I have to screen more?▾
Hardly at all. Going from 50 candidates to 500 — ten times the pile — raises the number you need to screen for 90% confidence from 18 to 22. Four more. Pool size affects who is available to find, not how deep you have to dig to find them.
Is this the 37% rule?▾
No, and the 37% rule does not apply to normal hiring. That result (the secretary problem) assumes you decide on each candidate immediately and irrevocably, can never go back to someone you passed on, and only care about landing the single best person. Real shortlisting lets you review a batch and then choose among all of it, which is a different problem with a different answer.
What if I need the single best candidate, not just a top-10% one?▾
That gets expensive fast. The chance that the best of your sample is the outright best of the pool is simply the fraction you screened — screen 30 of 200 and it is 15%. Being confident of the true number one means going through nearly everything, which is why most hiring targets a quality band instead.
Does screening more candidates improve my hire?▾
Only up to a point, and only if your screening is accurate. Volume decides how much of the pool you have seen; it does nothing for your ability to tell a strong candidate from a weak one. If your screening step cannot rank people reliably, going through more of them samples a pool you still cannot sort.
What numbers does this calculator use?▾
None but yours. There is no industry benchmark, multiplier, or survey figure anywhere in it — the result is exact probability arithmetic over the applicant count, quality bar, and review count you enter.
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Cite this tool
Kaairo — How Many Candidates Should You Interview? https://www.kaairo.ai/tools/how-many-candidates-to-interviewScreening depth is the easy half. Screening accuracy is the other one.
Kaairo scores candidates on demonstrated competencies rather than résumé keywords — so the ranking you get back reflects what people can actually do, which is the assumption this calculator rests on.