Every millilitre value in the app, the published research behind them, and a plain account of what this method cannot tell you.
The short version. PeriodVol converts the products you log into an estimate of blood lost, in millilitres, and compares your cycle total to the clinical 80 ml heavy-bleeding threshold. Those millilitre values are anchored to published research, not measured on you. PeriodVol is not a medical device, it does not diagnose anything, and it is not clinically validated. This page exists so you can judge the numbers yourself instead of taking our word for them.
Three steps, all of them on your own phone:
There is no account and no server. Nothing is transmitted, so none of this is calculated anywhere except on your device.
Worth being direct about, because it determines how much weight the number deserves.
An estimate that is honest about being an estimate is still far more useful than a shrug — which is the situation this app was built to fix. But it is an estimate.
The upper limit of normal menstrual blood loss is 80 ml per cycle. It comes from the foundational population study:
Hallberg L, Högdahl A-M, Nilsson L, Rybo G. Menstrual blood loss — a population study. Acta Obstetricia et Gynecologica Scandinavica, 1966;45(3):320–351.
That 80 ml figure is still the objective research definition of HMB, and it is what PeriodVol flags. Modern guidelines such as NICE NG88 additionally define HMB by its impact on quality of life — a person can be seriously affected below 80 ml. PeriodVol surfaces the objective number and leaves the diagnosis to a clinician.
The doctor report compares your logs against the four parameters FIGO defines, so volume is presented inside the vocabulary clinicians already use for abnormal uterine bleeding rather than as an isolated number.
| Parameter | Normal range | Abnormal |
|---|---|---|
| Frequency | every 24–38 days | < 24 or > 38 days |
| Duration | ≤ 8 days | > 8 days (prolonged) |
| Regularity | shortest–longest ≤ 7–9 days | greater variation |
| Volume | 5–80 ml per cycle | > 80 ml (heavy) |
PeriodVol's picture-based saturation logging follows the same principle as the Pictorial Blood Loss Assessment Chart (PBAC), a validated clinical tool in which products are recorded by saturation level and clots, and the resulting score estimates blood loss (Higham 1990). A PBAC score of 100 or more correlates with measured loss over 80 ml, with sensitivity and specificity above 80% in the original validation, though later studies report varying cut-offs.
PeriodVol differs by mapping each logged item straight to estimated millilitres rather than to arbitrary points — but the underlying pictorial-to-volume logic is the same evidence-based approach. You can score yourself the classic way with our PBAC calculator.
The pictorial family splits in two:
PeriodVol's model belongs with the millilitre-calibrated group. Like Wyatt and Magnay it reports estimated volume rather than abstract points, and its per-product values track the Wyatt 2001 figures closely — the night-pad scale is close to Wyatt's night-towel scale — while staying at the conservative, real-use end relative to the high-absorbency “ultra” products measured by Magnay 2014 and DeLoughery 2024. The doctor report also surfaces a PBAC-equivalent point score, so the output is legible to a clinician who thinks in either unit.
These are the estimated millilitres of blood per single product change, at each saturation level. They are exactly the values the app computes with — the code is the source of truth, and these tables are generated from it.
| Pad size | Light | Medium | Heavy | Saturated |
|---|---|---|---|---|
| Liner | 0.5 | 1.0 | 1.5 | 2 |
| Regular | 1.0 | 2.5 | 4.0 | 5 |
| Large | 2.0 | 4.0 | 7.0 | 10 |
| Night | 3.0 | 6.0 | 10.0 | 14 |
| Light | Medium | Heavy | Saturated | |
|---|---|---|---|---|
| Tampon | 1 | 3 | 5 | 7 |
Cups are marked with volume lines, so this is the most accurate input in the app: stated capacity × observed fill.
| Cup capacity | ¼ | ½ | ¾ | Full |
|---|---|---|---|---|
| 20 ml | 5 | 10 | 15 | 20 |
| 25 ml | 6 | 13 | 19 | 25 |
| 30 ml | 8 | 15 | 23 | 30 |
Not sure of your cup's capacity? See our menstrual cup capacity guide.
| Small clot | Large clot | |
|---|---|---|
| Estimated volume | 1 ml | 3 ml |
Clots contribute a small millilitre estimate, but the app also surfaces clot size and frequency separately, because large or frequent clots are an independent clinical signal regardless of the total volume. Our blood-loss chart guide covers how clot size is judged.
This is the single most important design decision in the app, and the one most worth understanding before you trust a total.
PeriodVol estimates the blood actually lost in typical use, which is deliberately lower than a product's maximum laboratory capacity.
The anchor rule: a fully soaked regular pad or tampon ≈ 5 ml of blood, so it takes roughly 16 fully soaked normal products to reach 80 ml. That comes from the Centre for Menstrual Cycle and Ovulation Research (CeMCOR) at the University of British Columbia, whose guidance puts a soaked normal product at about 5 ml and a super or maxi product at about 10 ml. That independently corroborates two of our values — the 5 ml regular-saturated anchor and the 10 ml large-pad-saturated estimate — and keeps cycle totals inside the physiologically realistic 30–80 ml range Hallberg established.
In 2023 a study tested real products with blood for the first time:
DeLoughery E, Colwill AC, Edelman A, Samuelson Bannow B. Red blood cell capacity of modern menstrual products: considerations for assessing heavy menstrual bleeding. BMJ Sexual & Reproductive Health, 2024;50(1):21–26.
It found modern products often hold far more than their labels suggest, with wide variation between them. But those are maximum saturation capacities — how much a product can hold when soaked to its limit — which is not how much blood is typically lost in one change.
We got this wrong ourselves. An earlier version of PeriodVol's model used maximum-capacity figures as if they were typical per-use loss, which overestimated real blood loss by roughly 3–6×. We corrected the values downwards on 17 June 2026. If you used the app before that date, your older cycle totals read higher than the current model would produce.
The net effect is that PeriodVol is tuned not to cry wolf. It is deliberately conservative about flagging heavy bleeding, so that an 80 ml flag means something instead of firing every cycle.
One cycle, logged:
Cycle total ≈ 54 ml → “Normal” — below the 80 ml line, above the 30–40 ml average. The app also shows the number of changes (14) and clots (1) as secondary signals, so the total is never the only thing you see.
The app limits the damage any one judgement can do by showing pictograms for each saturation level, and by surfacing the number of changes and the clot burden alongside the millilitre total, so no single estimate dominates the picture.
To move from “literature-anchored estimate” to “validated”, the credible steps would be:
None of that has been done. Until it is, PeriodVol is an evidence-anchored estimator, and we will keep describing it that way.
You log each product by type and how soaked it is; each combination maps to an estimated millilitre value, summed across the cycle and compared to 80 ml. It all runs on your device.
No. The figures are literature-anchored estimates, not measurements validated against the alkaline-haematin reference method in real users. It is not a medical device and does not diagnose.
Hallberg et al. 1966 — 476 women, blood loss measured by alkaline haematin. The mean was 30–40 ml and roughly 80 ml sat at the 95th percentile, so it became the upper limit of normal.
PeriodVol uses ~5 ml for a soaked regular pad or tampon and ~10 ml for a soaked large pad, so ~16 soaked normal products ≈ 80 ml. These are typical-use estimates, not laboratory maximums.
The earlier model used maximum product capacity as if it were typical per-use loss, overestimating by roughly 3–6×. It was corrected downwards on 17 June 2026 so that an 80 ml flag stays meaningful.
A cup is the most accurate input because you read the volume directly. Pad and tampon saturation is subjective and is the main source of variation between users, which is why changes and clots are shown alongside the total.