How to Measure Ring Size at Home: Guide & Charts

Ordering a ring online for yourself—or secretly measuring a partner’s finger before a proposal—feels simple until you realize the numbers don’t match. Most people guess their size, only to discover the ring slides off or won’t budge past the knuckle. Getting it right at home is easier than most realize, and you probably already have everything you need. Here’s how to measure ring size accurately without leaving the house.

Common home tool: paper strip or string ·
Measurement unit: millimeters circumference ·
Diameter formula: circumference divided by 3.14 ·
Finger position: base of finger snug fit

Use this table to cross-reference your measurement method against the key variables that affect accuracy and size selection.

How do you measure a ring size at home?

You can get a surprisingly accurate ring size using items already lying around the house—no specialty tools required. The key is measuring the right spot on your finger and converting that measurement to a size number. String, a paper strip, or a flexible measuring tape will all work, though each has trade-offs in precision.

Using paper strip

• Cut a thin strip of paper roughly 3mm wide
• Wrap it snugly around the base of your finger
• Mark where the paper overlaps
• Measure that distance in millimeters with a ruler
• Divide by 3.14 to get diameter, or match directly to a size chart

The advantage of paper is that it stays put once marked, making it easier to measure accurately. Wezoree recommends wrapping the base of the finger, marking the overlap, and then measuring in mm against a ring size chart.

Using string or thread

• Wrap string around the base of your finger
• Mark the point where it overlaps, or cut it there
• Lay the string flat and measure the length in mm
• Compare to the circumference column on a size chart
• Choose the larger size if you land between two numbers

The Knot notes that the string method is simple but prone to stretching—always cross-check with a second method before committing to a size.

Using measuring tape

• Use a flexible measuring tape or any strip with mm markings
• Wrap around the base of the finger
• Read the measurement directly
• Match to the circumference column on the size chart

Brilliant Earth recommends the tape method for precise fits, along with their free mailed ring sizer as a physical alternative that mimics the actual ring feel.

The pattern across these methods is consistent: measure circumference in mm, then convert to your target sizing system. Paper strips tend to hold their shape better after marking, while string is more prone to stretching—so cross-check when possible.

Can I measure ring size with my phone?

Phone apps offer a convenient alternative to physical methods, though they require careful setup before you get an accurate reading. Here’s what to know before you rely on them for your next ring purchase.

Phone camera apps

• Download a ring sizing app such as RingFit for Android or RingSize.app
• Calibrate the screen using a known object—a US Quarter, 1 Yuan, or similar standard coin
• Place your ring on the screen circle and adjust the slider to match the inner edge
• The app displays your size in US, UK, EU, or mm systems

RingSize.app requires screen calibration with a US Quarter or other standard coin before measuring. Once calibrated, it shows US, UK, and mm sizes. RingFit claims 0.01 mm precision after calibration, according to its Google Play listing.

“Our free ring size app features an actual ring size chart on screen that you can use to measure your ring size instantly.”

— RingSize.app developer

AR ring sizers and printable sizers

• Some apps use augmented reality to scan your finger directly
• Others generate printable sizers for you to cut out and try on
• Always print at 100% scale and verify with a ruler before cutting

Laine Jewellery recommends RingFit for Android users and notes it displays size alongside mm diameter. The RingSizer app supports EU, US, UK, JP, and mm systems for international shoppers.

“Methods that include the String Method, Tape Measure, or basing your ring size off of your shoe size… don’t work.”

— Hannah Naomi Jewelry studio

What size ring is 7 cm?

Converting circumference to standard sizes becomes simple once you know the formulas. Here’s how 7 cm breaks down across the main sizing systems.

7 cm in US sizes

7 cm equals 70 mm circumference. Converting to diameter: 70 mm ÷ 3.14 = approximately 22.3 mm. US size 11 typically corresponds to 21.8 mm diameter, while US size 11.5 is around 22.2 mm. Blue Nile’s chart confirms that multiplying diameter by 3.14 gives you the circumference needed for chart matching.

7 cm in EU sizes

EU sizing uses mm circumference directly. 70 mm corresponds to EU size 70, or approximately EU size 52 for some brands. Wezoree recommends multiplying ring diameter by 3.14 (pi) to get circumference for chart matching.

The implication: size conversions matter most when purchasing internationally or from brands with non-US sizing systems—a half-size error on a wide band means the difference between comfortable and too tight.

How do I know my ring size by number?

Different countries use entirely different numbering systems—US, UK, and EU all have their own scales. Here’s how to read and convert between them so you never buy the wrong size again.

US numeric sizing

US sizes range from 1 to 13+, with the size based on circumference in mm. The internal diameter of a US size 6 is roughly 16.5 mm, while a US size 9 sits around 19.2 mm. Most US jewelers use mm-based internal diameter as the reference point for their numeric scale. Brilliance.com provides ring size charts that convert across US, UK, and international systems.

UK letter sizing

The UK uses letters from A to Z, with each letter corresponding to a specific mm circumference. A UK size L is approximately 52 mm circumference—equivalent to a US size 6. Conversion charts make the math straightforward once you know which system you’re starting from.

How to size a Bvlgari ring?

Bvlgari uses EU sizing, which catches many buyers off guard because EU numbers are much larger than US numbers. Here’s how to find your equivalent without guessing.

Bvlgari size 52 equivalent

Bvlgari size 52 corresponds to 52 mm circumference—which is roughly a US size 6. This is a critical distinction: a US size 52 would be enormous, while Bvlgari’s size 52 is a standard mid-size. Always check the brand’s own conversion chart before purchasing.

Official Bvlgari charts

Bvlgari provides official sizing guides that convert their EU sizes to US, UK, JP, and other international systems. Pillar Styles’ 2024 update on home measuring methods emphasizes checking brand-specific charts for high-value purchases. For luxury rings, the small cost of getting it right the first time is worth the peace of mind.

The catch: EU sizing catches buyers off guard because the numbers run much higher than US equivalents—a US size 52 would be enormous, while Bvlgari’s size 52 is a standard mid-size.

Related reading: 95 kg in Stone · 156 cm in Feet

For surprise proposals or online jewelry orders, this accurate home measurement guide shares precise techniques using string or paper to avoid resizing fees.

Frequently asked questions