Find out how much you've spent on the so-called tampon tax - the VAT on sanitary products.
Tampons and towels are currently taxed at 5% in the UK. But they have been subject to five different rates since 1973.
So how much you've spent depends on how old you are and when you started your first period.
Try our calculator to see roughly what you've spent so far, and how much you might spend in your lifetime.
All figures are in current prices. The lifetime VAT calculation assumes a continued rate of 5%.
Can't see the calculator? Click here.
How the calculator works
The calculator is based on a number of assumptions:
- You have 13 periods a year with a 28-day cycle - although periods can range from 21 to 35 days
- You use 22 tampons and/or towels per cycle
- You will go through, or went through, menopause at age 51
- Tampons and towels cost 13p per unit
Biological figures are based on information from NHS UK. The unit cost is an average calculated on today's prices, courtesy of mysupermarket.co.uk, from three leading UK retailers (not including those which have already reduced their prices by 5% to cover the tampon tax).
We reached your result by calculating how many years you were menstruating for during each of the five VAT rates that have applied to sanitary products since 1973 and how many years you are likely to continue to menstruate, assuming that menopause is at age 51.
All calculations are in whole years, from 1 January of the year you entered.
For simplicity, we have not taken pregnancy or other reasons for missing periods into the calculation.
The figure of 22 products used per cycle is from the Absorbent Hygiene Products Manufacturers Association and the Women's Environmental Network.
A brief history of the tampon tax
Value Added Tax is currently charged at the reduced rate of 5% on sanitary products, including panty liners and certain maternity pads. But this hasn't always been the case.
The UK first introduced VAT in 1973 when it joined the European Economic Community, with a standard rate of 10% - which applied to sanitary products.
In summer 1974, standard VAT was cut to 8%, before rising to 15% in 1979 and 17.5% in 1991.
The Labour government moved sanitary products on to a reduced rate of 5% from January 2001, following a campaign and debates in parliament.
This is currently the lowest rate possible under the EU's VAT rules.
In 2015, activist Laura Coryton created a petition calling for the UK government to introduce a zero-rate for the products, which gained more than 320,000 signatures.
That October, the government confirmed it would seek a change in EU law to allow any rate of VAT to be applied to sanitary protection, as part of a review of VAT rates to be undertaken by the European Commission in 2016.
And the then Chancellor George Osborne announced in the 2015 Autumn Statement that the funds raised by VAT on tampons and towels would be donated to women's health and support charities. This sum was worth £15m in 2016-17.
In July this year, supermarket Tesco cut prices on nearly 100 menstrual protection products in order to shoulder the 5% VAT cost.
Competitors Waitrose and Morrisons followed suit in August and other retailers have pledged to pass on a price cut if VAT becomes zero-rated.
Future of the VAT rate
The European Commission says it is aiming to bring in a zero rate for sanitary products in 2018 and the UK government has already legislated to allow this to happen as soon as rules change.
But for now, tampons and towels will be continue to be charged for VAT at the same rate as solar panels, child car seats and nicotine patches.
Produced by Becca Meier, Bella Hurrell and Christine Jeavans, with additional research by Catherine Bean. Design by Zoe Bartholomew and Sumi Senthinathan. Development by Joe Reed and Evisa Terziu.