Calibrate once, measure anything
A browser does not know how big your screen is. Match an outline to a bank card once, and every tool here is true to size on this device — with the margin of error shown, not hidden.
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Ring Sizer
Lay a ring on the screen, read five size systems.
Calibrate once with a bank card, lay a ring on the circle and read its size in Indian, US, UK, EU and Japanese sizes — with a full conversion chart and a printable paper sizer. Nothing is uploaded.
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Bangle Sizer
Lay a bangle on the screen, or measure your hand.
Calibrate once with a bank card, lay a bangle on the circle and read its Indian size, 2-2 to 3-0, kadas included. No bangle? Type your hand measurement instead. Nothing is uploaded.
Open the tool - Live
Online Ruler
A real-size ruler, once you match a card.
Match an outline to any bank card and the ruler is true to size on your screen, in cm, mm and inches, across or upright. The calibration stays on your device and every measuring tool here reuses it.
Open the tool
Each opens ready for the job
How measuring on a screen works
Calibrating with a bank card
A screen does not know its own physical size, so a ruler drawn at a fixed number of pixels is wrong on almost every device. Every bank, debit and ID card is made to the same ISO standard size, 85.6 mm by 53.98 mm. Hold a card to the screen, match the outline to it, and the page knows how many pixels make a millimetre on your display. The calibration is kept on your device, and every measuring tool here reuses it.
The ruler, the ring sizer and the bangle sizer
The Online Ruler measures in centimetres, millimetres and inches, across the screen or upright. The Ring Sizer has you lay a ring that already fits on a circle and adjust it to the inside edge; it then reads the size in Indian, US, UK, EU and Japanese sizes, with a full conversion chart. If you cannot use a screen, it also prints a paper sizer to wrap around a finger.
The Bangle Sizer works the same way with a bangle or kada and reads the Indian size, 2-2 to 3-0. With no bangle to hand, type the measurement round your hand, thumb tucked in, and it gives the smallest size that will pass over it.
How accurate it is
Once calibrated, the measurement is only as good as how closely you matched the card outline, so take your time over that step. For a ring, a millimetre of diameter is roughly one size, so measure twice, at the end of the day when fingers are largest, and choose the bigger size if you land between two. The guides below cover measuring without a ruler and finding a ring size without asking.
Before you open one
How can a screen measure in real centimetres?
You calibrate it once with any bank, debit or ID card, which are all made to the same ISO size of 85.6 by 53.98 mm. The page then knows how many pixels make a millimetre on your screen.
Which ring sizes does the ring sizer show?
Indian, US, UK, EU and Japanese sizes, with a full conversion chart. It also prints a paper sizer to wrap round a finger.
What if I do not have a bangle to measure?
Type the measurement round your hand with the thumb tucked in, and the bangle sizer gives the smallest Indian size, from 2-2 to 3-0, that will pass over it.
How accurate is it?
As accurate as your match to the card outline. For a ring, a millimetre of diameter is about one size, so measure twice and pick the bigger size if you land between two.
Guides for these tools
Bangle size chart (India): inches, mm and hand size
Every Indian bangle size from 2-0 to 3-0 with the inner diameter in inches and mm, the inside circumference, and the largest hand each size passes over.
6 min readATM and credit card size in cm, mm and inches, and how to use a card as a ruler
Every ATM, debit and credit card is 8.56 × 5.398 cm (85.6 × 53.98 mm, or 3.370 × 2.125 inches). How to measure with one and set a screen ruler.
5 min readHow to find someone's ring size secretly: five ways that work
Five ways to get a partner's ring size without asking, from borrowing a ring for a minute to asking a friend, ranked by accuracy, with mistakes to avoid.
6 min readHow to measure bangle size at home: three ways, best first
Measure a bangle you own on a calibrated screen, measure your hand with the thumb tucked in, or use a ruler. Which size to pick when you fall between two.
6 min readIndian ring size chart, with US, UK and EU sizes side by side
What an Indian ring size measures, the full conversion to US, UK and EU sizes with diameters in mm, and why two jewellers' charts can disagree by a size.
6 min readKada size for men: how to measure it, and the size chart
Kada sizes use the same 2-N scale as bangles. How to measure a kada or your hand at home, the sizes in inches and mm, and how loose a kada should sit.
5 min read
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