How this instrument works
Semen analysis is a standard laboratory test used in the male fertility workup, reporting volume, sperm concentration, total sperm number, motility, and morphology. The World Health Organization periodically updates the reference ranges labs compare these values against, based on data collected from men whose partners became pregnant within about a year of trying; the 6th edition of its laboratory manual, published in 2021, set the reference limits in current use.
Those reference limits are 5th-percentile lower bounds, not pass/fail cutoffs for infertility. A 5th-percentile lower reference limit means that, in the reference population of fertile men the WHO studied, only about 5% had a value below that number — so roughly 95% of that fertile population sat at or above it, but a small fraction of men who did father a pregnancy still fell under one or more limits. Falling below a limit is a statistical flag worth a closer look, not a diagnosis of infertility on its own.
Semen parameters also vary between samples from the same person — abstinence period before the sample, recent illness, and normal biological variability can all shift the numbers — which is one reason clinical guidance generally recommends evaluating at least two samples before drawing conclusions. This calculator only compares the six values entered against the WHO 2021 limits and counts how many fall below them; it doesn't interpret the result, account for repeat testing, or weigh the many other factors — on both partners' sides — that determine fertility.
- Enter semen volume, in mL.
- Enter sperm concentration (million/mL) and total sperm number (million/ejaculate).
- Enter total motility, as a percentage.
- Enter progressive motility, as a percentage.
- Enter normal morphology, as a percentage.
- Read which of the six values fall below the WHO 2021 lower reference limit, and the total count out of six flagged.
Worked example — three samples across the reference range
A sample with volume 2 mL, concentration 20 million/mL, total count 45 million, total motility 50%, progressive motility 35%, and morphology 5% sits at or above all six WHO 2021 lower limits — 0 of 6 flagged.
A sample with volume 1 mL, concentration 10 million/mL, total count 15 million, total motility 30%, progressive motility 20%, and morphology 2% falls below every one of the six limits — 6 of 6 flagged.
A sample sitting exactly at each lower limit — 1.4 mL, 16 million/mL, 39 million, 42% total motility, 30% progressive motility, 4% morphology — flags 0 of 6. These are 5th-percentile lower bounds, so a value exactly at the limit still counts as within range; only falling strictly below a limit trips its flag.
Questions
Does a flagged value mean I'm infertile?
No. These are 5th-percentile lower reference limits drawn from a population of fertile men, not diagnostic cutoffs — a small share of men who went on to father a pregnancy still had at least one value below these limits. Being flagged on one or more parameters is a reason for a clinician to look closer, not a standalone infertility diagnosis.
Why do semen analysis results vary between samples from the same person?
Sperm production and semen quality can shift meaningfully with the length of abstinence before the sample, recent illness or fever, stress, and ordinary biological variability. That variability is why evaluating at least two samples, typically weeks apart, is generally recommended before drawing conclusions from a single test.
What changed in the WHO's 6th edition (2021) reference values?
The 6th edition updated the reference population used to derive the lower limits and reintroduced a four-category classification of sperm motility (progressive, non-progressive, immotile, plus a category for local/vibratory movement), refining how motility is assessed compared with the prior (5th) edition from 2010.
What's the difference between total motility and progressive motility?
Total motility is the percentage of sperm showing any movement at all. Progressive motility is the subset moving purposefully in a fairly straight line or large circle — the pattern considered most relevant to reaching an egg — so progressive motility is always a percentage of, and typically lower than, total motility.
Is total sperm number the same as concentration?
No. Concentration is sperm per milliliter of semen. Total sperm number multiplies that concentration by the full ejaculate volume, giving the total number of sperm in the sample rather than a per-mL density — a low-volume sample can have a normal concentration but a low total count, or the reverse.
Can this calculator diagnose a fertility problem?
No. It only compares six numeric values against the WHO 2021 lower reference limits and counts how many fall below them. A fertility evaluation also involves repeat testing, the partner's evaluation, hormone levels, medical and reproductive history, and physical examination — none of which this tool assesses.
Who typically orders a semen analysis?
It's a standard first-line test in a male fertility workup, usually ordered by a urologist, reproductive endocrinologist, or primary care clinician when a couple has been trying to conceive without success. It's also used for other purposes, such as confirming vasectomy success.
References
- World Health Organization — WHO Laboratory Manual for the Examination and Processing of Human Semen, 6th edition (2021)
- Evolution of the WHO 'Semen' processing manual from the first (1980) to the sixth edition (2021) — PubMed
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.