Expertise you can trust: The Juyoyo team, a handcrafted fine jewelry brand specializing in gemstones and precious metals, created this article to share practical, research-based insights drawn from years of hands-on experience in jewelry design, material selection, and quality evaluation, helping readers better understand jewelry craftsmanship, materials, value, and care.

How to Know Ring Size Without Measuring: 5 Secret Ways to Keep the Surprise

Jan 13,2026 | Juyoyo

how to know ring size without measuring

Quick Look: How to Find a Ring Size Without Measuring

There are two methods you can use to find a ring size without measuring:

Existing Ring
String/Paper Test
Asking friends
Consulting a jeweler

The most accurate way? Secretly borrowing a ring they wear on their ring finger and matching it against a Juyoyo printable sizing chart.

Staring at a stunning engagement ring online but stuck on the final, most crucial detail: the ring size. You may wonder how to know a ring size without measuring it. It's a common problem, but it's solvable! Based on professional jewelry sizing principles, this guide offers five discreet and practical ways to get a ring size at home without a measuring tool.

Method 1. Use an Existing Ring (The Most Accurate Way)

If your partner already wears rings, then you know their ring size.

Here's how to do it step by step:

Borrow & Select: Borrow a ring that they wear on the target finger. Make sure it's a ring they wear on their fourth finger.

Expert tip: If they are right-handed, their right ring finger is likely 0.5 sizes larger than their left.

Trace the Inside: Place the ring flat and measure its inner diameter (not its outer width) across its widest point.

Warning: Never trace the outside of the ring. Band thickness varies significantly between styles; tracing the outside will result in a ring that is far too large.

Use a Ring Size Chart: If you cannot measure directly, place the ring on a printable, 100% scale ring chart and trace the inside to find the matching circle. Then, write down the measurement in millimeters (mm). Be sure your printer is set to 100% and not "fit to page."

2. String/Paper Method (Easy, Good Estimate)

If they don't wear rings, the string method is the classic DIY backup. It works best while they're sleeping or as a "game" with a piece of ribbon. All you need is a piece of non-stretchy string, a narrow strip of paper, a pen, and a ruler.

The Stealthy Steps:

Wrap: Take a piece of non-stretchy string or a thin strip of paper. Wrap it around the base of your finger.
Mark: Use a fine-point pen to mark exactly where the string overlaps.
Measure: Lay the string flat against a ruler and measure the distance in millimeters (mm). This is the circumference.

The Conversion (Don't Worry, It's Simple):

You’ll use this formula: Diameter = Circumference ÷ 3.14 (π).

Example: If the marked length is 52 mm, then 52 ÷ 3.14 = 16.56 mm diameter. This is roughly a US size 6.

Juyoyo Expert Tip: Always measure the knuckle as well. If the base of your finger is much thinner than your knuckle, choose a size between the two measurements to ensure your ring can slide on.

Inner Diameter / Diameter (mm)	US Ring Size	Notes
14.1 mm	3
14.5 mm	3.5
14.9 mm	4	Common starting point for women
15.3 mm	4.5
15.7 mm	5
16.1 mm	5.5
16.5 mm	6	Most Common Average Ring Size for Women
16.9 mm	6.5
17.3 mm	7	Common upper range for women
17.7 mm	7.5
18.1 mm	8	Typical threshold between women's & men's sizes
18.5 mm	8.5
18.9 mm	9	Most Common Average Ring Size for Men
19.3 mm	9.5
19.7 mm	10
20.1 mm	10.5
20.5 mm	11
20.9 mm	11.5
21.3 mm	12
21.7 mm	12.5
22.1 mm	13

3. Ask Friends or Family (Good for Surprise Proposals)

Sometimes the best tool is a trusted ally. A best friend, sibling, or parent may already know the answer or can help you find out without arousing suspicion.

How to approach:

Pick someone who can keep a secret—a single slip can ruin the proposal. Be explicit: "This is confidential."

Ask someone who has shopped for jewelry with the person before, such as a close friend, sibling, or parent. They may know the ring size or remember what was tried on at a store.

4. Photo Comparison (Best as a Last-Resort Estimate)

In the age of AI, "photo sizing" is becoming more popular. While not as accurate as a physical measurement, it can narrow down the range.

Here's how you can do it:

Locate a photo in which your hand is positioned next to an object you recognize, such as your phone, a coin, or your credit card.
Measure the dimensions of the object in the photo to create a pixel-to-millimeter scale, and then estimate the width of the finger.

Limitations: Lens distortion, camera angle, and cropping can introduce errors. While not perfectly precise, this method can help you rule out sizes that are extremely inaccurate and is a clever use of existing resources.

5. When DIY Isn’t Enough: Why You Should See a Jeweler for Professional Sizing

Consider this option if you have wide bands, non-round rings, full-eternity settings, or unusual finger anatomy.

What a jeweler can do:

Provide precise measurements with professional tools.
Advise on whether a ring is resizable. One or two sizes can resize most plain bands, but eternity bands and complex pavé settings often cannot be.
Provide temporary sizing solutions, such as adjusters or half sizes, while the permanent size is being finalized.

This method ensures the highest level of accuracy and is recommended if a near-perfect fit is required or if the ring design limits resizing.

Reference Data: Average Ring Sizes

Average ring sizes should only be used as a last resort. However, they can provide a general starting point if no other information is available.

Gender	Average US Size	Common Range	Average Inside Diameter (mm)
Women	6	5 to 7	16.5 mm
Men	9	8 to 10	19.0 mm

Note: For international customers, a US size 6 is approximately equivalent to a UK size L½ or a EU size 52.

Pro Tips for Getting it Right

These insider insights can mean the difference between a "good guess" and a "perfect fit."

Time of Day: Measure mid-afternoon or early evening because fingers swell with activity and heat.
Dominant Hand: The dominant hand is often ½ size larger, so size the correct hand.
Rather Bigger Than Smaller: If you must choose between two sizes, buy the larger one if the ring is resizable, because it's harder to fix if it's too small.
Wide Bands: Add 0.25-0.5 sizes for bands wider than 6 mm.
Three-Day Verification: Measure three different times over three days and take the average.

What to Do if the Size is Wrong?

First, don't panic. At Juyoyo, we understand that surprises can be tricky. Ring resizing is a common service.

Easy to Resize: Simple metal bands (gold, silver, and platinum) and solitaire engagement rings are usually easy to resize.
Difficult or Impossible to Resize: Eternity bands with diamonds all around, rings made of tungsten or ceramic, and rings with intricate, continuous patterns on the shank are often not resizable or very costly to resize.

Discover the actual cost of getting a ring resized.

The Final Word

For optimal results, utilize the existing-ring method in conjunction with the ring size chart whenever feasible. If secrecy is a concern, use a combination of methods (friend intel, string method, and photo comparison) and follow the "bigger rather than smaller" rule. If precision matters, see a jeweler.

Juyoyo stands behind every ring, providing clear resizing guidance and customer support to help you achieve the perfect fit. And if you're ready to put this secret knowledge to the test, explore our stunning collection of gemstone rings, where each piece is designed with the same care and flexibility to make your surprise moment truly unforgettable.

Ring Size FAQ

How to Know Ring Size Without Measuring at Home?

Use a printable chart with an existing ring, the string/paper method, or ask a friend. Then, verify the size using the 3-day method.

Which Method Is Best for Finding Ring Size?

Borrowing an existing ring and measuring the inner diameter is the best method, but professional sizing is the most accurate.

Is It Better to Size Up or Down for a Surprise Ring?

It's better to size up slightly than to size down. A slightly larger ring is easier to resize and more comfortable than a ring that won't fit over the knuckle.

What is the Average Ring Size for Women?

Most commonly, US sizes 5-7 (size 6 is typical). However, average sizes should only be used as a last resort and should never replace actual measurement methods.

What is the Average Ring Size for Men?

Most commonly, US sizes 8-11 (size 9 is typical). Average sizes should also only be used as a last resort and never replace actual measurement methods.

Can a Ring Be Resized?

Most gold, silver, and platinum rings can be resized. However, eternity bands and rings made of alternative metals, such as tungsten or cobalt, typically cannot be resized.