Menstrual & Cycle Health
Period Blood Loss Calculator
This calculator estimates how much blood you lose over a period. You can count your pads and tampons day by day and say how soaked each one was, add up the millilitres in your menstrual cup or disc, or work out a PBAC score, the points chart many clinics use. Nothing you enter is saved or sent anywhere.
Your result is a rough range, not a measurement. You'll see how it compares with the typical 30 to 40 ml and with the 80 ml line researchers use for heavy periods. The questions below the calculator matter just as much: doctors judge heavy periods mostly by how they affect your life.
What you used
Day 1
| Product | Lightly stained | About half soaked | Fully soaked |
|---|---|---|---|
| Regular pad | |||
| Large pad (super, maxi or overnight) | |||
| Regular tampon (light or regular) | |||
| Large tampon (super, super plus or ultra) |
Day 1
| Product | Lightly stained | Moderately stained | Completely soaked |
|---|---|---|---|
| Pads | |||
| Tampons |
about the size of a nickel coin or a grape
about the size of a half-dollar coin or a strawberry, or bigger
times blood leaked through or you had to change in a hurry
Do any of these apply to you?
Tick any that apply. They don't change your estimate.
Enter how many products you used to see an estimate.
When to get help
- Get medical help soon, before your next routine appointment, if you soak through at least one pad or tampon an hour for more than 2 hours in a row (Mayo Clinic).
- Soaking through two or more pads or tampons an hour for 2 to 3 hours in a row is a sign to see your provider or seek emergency care (Cleveland Clinic).
- Get emergency medical care right away if you're changing pads or tampons every hour for more than 2 hours in a row and you also have chest pain, shortness of breath, or feel lightheaded or dizzy (ACOG).
- After giving birth, soaking through two pads an hour for more than 1 to 2 hours, passing large clots, or feeling faint, dizzy or weak can be signs of heavy bleeding after birth. Call your doctor or midwife right away (ACOG, RCOG).
- Contact your midwife or GP if bleeding after birth gets heavier, smells unpleasant, or you feel unwell (RCOG).
- If you could be pregnant and have heavy bleeding, contact a doctor or midwife promptly.
How much blood do you lose on a period?
Less than most people think. The NHS says you'll lose about 20 to 90 ml during a period, which is about 1 to 5 tablespoons, although some women bleed more heavily than this. An NHS trust leaflet puts a typical period at 30 to 40 ml, or six to eight teaspoonfuls. Researchers at the University of Edinburgh give a normal range of 5 to 80 ml.
Most of it comes early. The NHS says bleeding tends to be heaviest in the first 2 days, and a period usually lasts about 5 days.
| Amount | Roughly | What it means |
|---|---|---|
| 5 ml | 1 teaspoon | about one soaked regular pad or tampon |
| 30–40 ml | 6–8 teaspoons | a typical whole period |
| 80 ml | about 5 tablespoons | the line researchers use for heavy periods |
The 80 ml figure comes from a 1960s Swedish study of 476 women. Its authors linked losses above 80 ml with iron deficiency and used it as a critical limit. Researchers still use it to define heavy menstrual bleeding in studies.
But measuring ml is hard outside a lab, and the number isn't the whole story. The UK's NICE guideline defines heavy menstrual bleeding as blood loss that interferes with a woman's physical, social, emotional or material quality of life. It tells doctors to focus on improving that, rather than on blood loss itself.
How this calculator works
You can use whichever way of counting fits the products you use. Each tab keeps its own entries.
Pads and tampons. Enter how many products you used each day and how soaked each one was. We use an estimate from the Centre for Menstrual Cycle and Ovulation Research (CeMCOR) at the University of British Columbia: a fully soaked regular pad or tampon holds about a teaspoon of blood (5 ml), and a super or maxi product holds about two teaspoons (10 ml). A half-soaked product counts as half. A lightly stained one counts as a tenth; that last figure is our own assumption.
The top of your range is double the bottom. That's also our assumption, because lab tests show modern products can hold far more than a teaspoon when completely full.
Cup or disc. Enter the millilitres each time you empty it. The calculator adds up your total fluid, then estimates how much of it was blood (see the next section).
PBAC score. Enter how stained each pad or tampon was, plus clots and episodes of flooding. The calculator adds up the points the way a paper chart does.
Use more than one tab if you switch products during a period, then add the results together yourself.
Blood or fluid? Why your result is a range
Menstrual fluid isn't pure blood. It also contains fluid and tissue from the lining of the womb. In a 1985 study of 28 women, blood made up 36% of menstrual fluid on average. But it varied hugely between women, from under 2% to over 80%. Proportions stayed about the same across different days of the period. Blood made up a larger share for women using an IUD and a smaller share for those on the pill.
That's why the cup tab shows your total fluid first. It then shows estimated blood as a range from roughly a sixth to a half of that fluid. A cup total of 90 ml, for example, works out at about 15 to 50 ml of blood.
Product counts have the opposite problem. They estimate blood directly, but you're judging by eye how full each product was, and products vary in what they hold. The range is our way of being honest about that.
So treat the result as a rough guide to whether your loss is light, typical or heavy, not a precise reading. If your numbers are near the 80 ml line, how your period affects you matters more than which side of it you land.
How much does a pad, tampon, cup or disc hold?
Less than the packet absorbency might suggest, and more than older estimates assumed.
| Product | What's known |
|---|---|
| Tampons | In the US, absorbency labels are set by a lab test using saline, not blood: light up to 6 g, regular 6 to 9 g, super 9 to 12 g, super plus 12 to 15 g, ultra 15 to 18 g. |
| Pads and tampons, real use | CeMCOR estimates about 5 ml of blood in a soaked regular product and 10 ml in a super or maxi one. |
| Modern products, lab maximum | A 2024 lab study found tampons, heavy pads and cups held about 20 to 50 ml of blood when completely full. |
| Menstrual discs | Held the most in the same study: 61 ml on average, up to 80 ml. |
| Period underwear | Held the least: about 2 ml on average. |
The gap between the lab maximum and the CeMCOR estimate is why we show a range. Most people change a product well before it's completely full.
The US Food and Drug Administration (FDA) advises using the lowest absorbency you need and changing tampons every 4 to 8 hours. If a cup is part of your routine, the NHS lists emptying it more often than recommended as a sign of heavy periods.
What is a PBAC score?
PBAC stands for Pictorial Blood Loss Assessment Chart. It was published in 1990 by Higham, O'Brien and Shaw. You record each pad or tampon you use and how stained it is, and each one earns points.
| Item | Lightly stained | Moderately stained | Completely soaked |
|---|---|---|---|
| Pad | 1 point | 5 points | 20 points |
| Tampon | 1 point | 5 points | 10 points |
The version used by St. Jude Children's Research Hospital also gives 1 point for each small clot (the size of a nickel coin or a grape), 5 for each large clot (a half-dollar coin or a strawberry) and 5 for each episode of flooding. Our calculator uses the same points with text descriptions rather than the chart's pictures.
In the original study, a total of 100 or more picked out heavy bleeding with a sensitivity and specificity above 80%. A later review gives the figures as 86% and 89%.
The score has limits:
- The original chart recorded clots and flooding but gave them no points, so later versions differ.
- It progressively underestimated blood loss as periods got heavier.
- Across studies, its accuracy varied widely, with sensitivity from 58% to 99% and specificity from 7.5% to 89%.
- It was tested with specific pads and tampons, not cups, discs or period underwear.
A score of 100 or more is a reason to talk to a doctor, not a diagnosis. A score under 100 doesn't rule out heavy periods.
Signs your period may be heavy
You don't need to measure anything to spot heavy periods. The NHS says you may have heavy periods if you:
- need to change your pad or tampon every 1 to 2 hours, or empty your menstrual cup more often than recommended
- need to use 2 types of period product together, such as a pad and a tampon
- have periods lasting more than 7 days
- pass blood clots larger than about 2.5 cm (the size of a 10p coin)
- bleed through to your clothes or bedding
- avoid daily activities, like exercise, or take time off work because of your periods
- feel tired or short of breath a lot
The American College of Obstetricians and Gynecologists (ACOG) adds needing to change pads or tampons during the night, and clots as big as a quarter or larger.
Heavy periods are common. ACOG says about one third of women seek treatment for them. The NHS notes they may be normal for you, and that treatment can help if they affect your daily life.
Heavy periods can have many causes. The NHS says it can be normal to have heavy periods. Causes include fibroids, endometriosis, adenomyosis and pelvic inflammatory disease, as well as some medicines, such as anticoagulants. Rarely, they can be a sign of womb cancer. ACOG also lists bleeding disorders and blood thinners. A GP can check for these, starting with a few questions and usually a blood test.
If you use a cup or period underwear, be aware that counting changes can mislead. In a small 2025 trial of people with heavy periods, cups and underwear were changed less often than disposable products on the heaviest days, but leaked more.
When to see a GP, and when to get help fast
The NHS advises seeing a GP if:
- heavy periods are affecting your life
- you've had heavy periods for some time
- you have severe pain during your periods
- you bleed between periods or after sex
- you have heavy periods and other symptoms, such as pain when peeing, pooing or having sex
Some bleeding needs help sooner. Mayo Clinic advises getting medical help before your next scheduled check-up if bleeding soaks at least one pad or tampon an hour for more than 2 hours in a row. It says the same for bleeding between periods and any bleeding after menopause.
Cleveland Clinic says heavy periods aren't usually life-threatening, but can be if you lose too much blood. It calls bleeding through two or more pads or tampons an hour for 2 to 3 hours in a row a sign to see your provider or seek emergency care. ACOG advises seeking emergency medical care right away if you're changing pads or tampons every hour for more than 2 hours in a row and you also have chest pain, shortness of breath, or feel lightheaded or dizzy.
After giving birth, ACOG describes heavy bleeding as soaking through two pads an hour for more than 1 to 2 hours. It can happen up to 12 weeks after birth. ACOG advises calling your doctor right away if you have signs such as heavy or gushing bleeding, large clots, or feeling faint, dizzy or weak.
Heavy periods, iron and tiredness
Losing a lot of blood every month can drain your iron stores. ACOG says blood loss from heavy periods can lead to iron-deficiency anaemia. The NHS lists heavy periods among its causes.
According to the NHS, symptoms of iron deficiency anaemia can include:
- tiredness and lack of energy
- shortness of breath
- noticeable heartbeats (palpitations)
- paler than usual skin
- headaches
NICE recommends a full blood count test for all women with heavy menstrual bleeding. If it shows anaemia, the NHS says iron tablets are usually recommended, typically for about 6 months, along with treating the cause.
Feeling exhausted during or after your period is worth mentioning to a GP, even if your calculator result looks typical.
Heavier periods at different life stages
Periods can change through life, and the NHS says they can be heavy when you first start, after pregnancy or as you approach menopause.
Teens. Mayo Clinic says teenagers are most likely to have cycles without an egg release during the first year after their first period, and problems with ovulation are a known cause of heavy bleeding. ACOG says you may have a bleeding disorder if you've had heavy periods since you first started. It advises telling a doctor if you or a family member have a problem with blood clotting, or if you feel dizzy or faint.
Contraception. The NHS says periods may become heavier, longer or more painful after a copper IUD (the coil) is fitted, and this may improve after a few months. ACOG says this is especially likely during the first year. Hormonal options, such as the IUS, are among the NHS treatments for heavy periods.
After pregnancy. Bleeding after birth isn't a period. The Royal College of Obstetricians and Gynaecologists (RCOG) says it usually stops by the time your baby is 12 weeks old.
Perimenopause. In the years before menopause, the NHS says bleeding may get heavier or lighter. ACOG still lists bleeding that is heavier or lasts longer than usual among the kinds of bleeding that aren't normal, so it's worth getting checked.
After menopause. Mayo Clinic advises getting medical help for any vaginal bleeding after menopause, and ACOG says it's especially important to tell your gynaecologist about it.
Tracking for an appointment. Note the products you use, how soaked they are, any clots or flooding, how many days you bleed, and how your period affects your life. Bring this calculator's results with you. More tools are on our Menstrual & Cycle Health calculators page and our Women's Health calculators page.
Frequently asked questions
Most people lose about 20 to 90 ml, according to the NHS, which is roughly 1 to 5 tablespoons. An NHS trust leaflet gives 30 to 40 ml as typical. Researchers usually call more than 80 ml heavy. What matters most is whether your bleeding affects your daily life.
Yes, 80 ml is the line researchers use for heavy menstrual bleeding. It comes from a 1960s Swedish study that linked losses above 80 ml with iron deficiency. In everyday practice, doctors focus more on how your periods affect you, because ml are hard to measure at home.
About a teaspoon, or 5 ml, for a fully soaked regular product, according to CeMCOR. A super or maxi product holds about 10 ml. Lab tests show modern heavy products can hold 20 to 50 ml when completely full, so real amounts vary.
There's no single daily limit. The NHS lists changing your pad or tampon every 1 to 2 hours as a sign of heavy periods. Mayo Clinic advises getting medical help soon if you soak at least one an hour for more than 2 hours in a row.
Read the millilitre marks on your cup or disc before emptying it, and write down each amount. Add them up over your period. Remember this is menstrual fluid, not pure blood: in one study, blood made up about a third of it on average. Try our Menstrual Cycle Calculator to keep track of when each period starts.
No. Menstrual fluid contains blood plus fluid and tissue from the lining of the womb. In a 1985 study, blood was 36% of the fluid on average, but it ranged from under 2% to over 80% between women. That's why cup results are shown as a range.
A PBAC score adds up points for each pad or tampon by how stained it is, plus clots and flooding. A total of 100 or more is the cut-off most often used in research for heavy bleeding. It's a screening number, not a diagnosis.
It gives a rough range, not a measurement. Only lab tests can measure blood loss exactly. Product estimates depend on how full you judge each one to be, and cup results include fluid that isn't blood. Use the result as a guide to discuss with a doctor.
The NHS lists passing clots larger than about 2.5 cm, the size of a 10p coin, as a sign of heavy periods. ACOG and Mayo Clinic use clots as big as a quarter or larger. If you often pass large clots, mention it to a GP and note their size.
ACOG advises emergency care right away if you change pads or tampons every hour for more than 2 hours and also have chest pain, shortness of breath, or feel lightheaded or dizzy. Cleveland Clinic says bleeding through two or more an hour for 2 to 3 hours needs a provider or emergency care.
Yes. ACOG says blood loss from heavy periods can lead to iron-deficiency anaemia, and the NHS lists heavy periods as a cause. Symptoms include tiredness, shortness of breath, palpitations and pale skin. NICE recommends a full blood count test for everyone with heavy menstrual bleeding.
Changing hormone levels can make periods less predictable. The NHS says bleeding may get heavier or lighter during perimenopause, and ACOG lists bleeding that is heavier or lasts longer than usual as not normal. Any bleeding after menopause should be checked by a doctor, Mayo Clinic and ACOG say. Try our Menopause Age Calculator to estimate when menopause may begin.
A copper IUD can. The NHS says periods may become heavier, longer or more painful after it's fitted, often improving after a few months. ACOG says this is especially likely in the first year. ACOG also says some hormonal birth control methods can lighten menstrual flow. Try our Contraceptive Effectiveness Reference to compare how well different methods work.
They can be. Mayo Clinic says teens are most likely to have cycles without an egg release in the first year, which can affect bleeding. But ACOG says heavy periods since your very first one may signal a bleeding disorder, and advises seeing a doctor if you feel dizzy or faint.
No. Bleeding after birth comes from where the placenta was attached, and the RCOG says it usually stops by the time your baby is 12 weeks old. ACOG says soaking through two pads an hour for more than 1 to 2 hours is a sign of heavy bleeding after birth, and to call your doctor right away.
Sources
- NHS, Heavy periods.
- NHS, Periods.
- NHS, Iron deficiency anaemia.
- NHS, Perimenopause and menopause symptoms.
- NHS, Side effects of an IUD.
- NICE guideline NG88, Heavy menstrual bleeding: assessment and management.
- Wirral University Teaching Hospital NHS Foundation Trust, Heavy periods (patient leaflet).
- ACOG, Heavy Menstrual Bleeding (FAQ).
- ACOG, Heavy and Abnormal Periods (FAQ for teens).
- ACOG, Abnormal Uterine Bleeding (FAQ).
- ACOG, Perimenopausal Bleeding and Bleeding After Menopause (FAQ).
- ACOG, 3 Conditions to Watch for After Childbirth.
- RCOG, Heavy bleeding after birth (postpartum haemorrhage).
- Mayo Clinic, Heavy menstrual bleeding: symptoms and causes.
- Cleveland Clinic, Menorrhagia (heavy menstrual bleeding).
- Centre for Menstrual Cycle and Ovulation Research (CeMCOR), Very heavy menstrual flow.
- University of Edinburgh HOPE, Normal menstruation.
- US eCFR, 21 CFR 801.430, User labeling for menstrual tampons.
- FDA, The facts on tampons and how to use them safely.
- Hallberg L, et al. Menstrual blood loss: a population study (Citation Classic commentary, 1986).
- Higham JM, O'Brien PM, Shaw RW. Assessment of menstrual blood loss using a pictorial chart. BJOG 1990. (abstract only)
- St. Jude Children's Research Hospital, Pictorial Blood Loss Assessment Chart.
- Magnay JL, et al. Pictorial methods to assess heavy menstrual bleeding in research and clinical practice: a systematic literature review. BMC Womens Health 2020.
- Magnay JL, et al. A systematic review of methods to measure menstrual blood loss. BMC Womens Health 2018.
- Fraser IS, et al. Blood and total fluid content of menstrual discharge. Obstet Gynecol 1985. (abstract only)
- DeLoughery E, et al. Red blood cell capacity of modern menstrual products. BMJ Sex Reprod Health 2024. (abstract only)
- Samuelson Bannow B, et al. Reusable menstrual hygiene products may lead to underdiagnosis of heavy menstrual bleeding: a randomised trial. BMJ Sex Reprod Health 2025. (abstract only)