How to Measure Your Ring Size Accurately (Even When It Changes)

Last updated: August 2025

Finding the right ring size sounds simple. Until the ring arrives and doesn’t fit. Whether you’re shopping for secondhand jewellery or investing in an antique piece, knowing your correct size is key to avoiding disappointment.

But here’s the thing. Ring sizing isn’t always exact. Your fingers can change throughout the day, and even the style of the ring can affect how it fits. This guide will help you measure your ring size accurately and understand the factors that might affect it. Especially when buying preloved or vintage jewellery online.

Table of Contents

• What’s the Best Way to Measure Ring Size at Home?
• When Should You Measure Your Finger?
• Why Ring Sizes Can Still Vary
• Should I Size Up for Wide Rings?
• How Secondhand & Antique Rings Can Differ
• What’s the Most Accurate Sizing System?
• FAQs
• Final Thoughts
• About Ps Its Vintage

What’s the Best Way to Measure Ring Size at Home?

The most accurate at-home method is to use a plastic ring sizer or a set of metal sizing rings, which you can buy online. These mimic how a real ring will feel on your finger.

If you don’t have tools, you can:

• Measure a ring that already fits you using a ruler (inner diameter in mm)
• Use the ring size calculator and international chart
• Try a printable ring size chart, but be cautious with printer scaling

For best results, measure a few times over a few days and take the average.

When Should You Measure Your Finger?

It’s best to measure:

• At the end of the day, when your fingers are at their largest
• In a room with a normal temperature
• When you're calm and haven’t just exercised or showered

Tip: Avoid measuring straight after showering, swimming, or heavy activity. Your fingers may swell temporarily.

Why Ring Sizes Can Still Vary

Even if you measure carefully, your ring size can fluctuate. Here’s why:

• Temperature: Heat causes swelling. Cold contracts your fingers.
• Water retention: Salt intake, hydration, or medication can affect swelling.
• Time of day: Fingers are smaller in the morning, larger in the evening.
• Band width: Wider bands feel tighter and may require sizing up.
• Health conditions: Pregnancy, arthritis, or circulation issues can cause size variation.

Should I Size Up for Wide Rings?

Yes. If the band is thick (such as a signet or wide stacking ring), consider going ½ a size up for comfort. Narrower bands tend to feel looser.

How Secondhand & Antique Rings Can Differ

Preloved and antique rings don’t always follow modern sizing. You might find:

• Older rings may be slightly oval due to years of wear
• Hallmarked pieces from outside the UK may use different systems
• Some rings may have been resized, affecting symmetry or fit

Always check the inner diameter in mm and use a conversion chart when buying internationally.

What’s the Most Accurate Sizing System?

The ISO 8653:2016 standard is the most accurate and internationally recognised method. It uses the inner diameter in millimetres to give a consistent base for UK, US, EU, and JP sizing systems.

You can try it using the free ring size calculator.

FAQs

How do I measure my ring size at home accurately?

Use a plastic ring sizer or measure the inside diameter (mm) of a ring that fits well. Avoid using string or paper — they stretch and give inconsistent results.

Do fingers swell during the day?

Yes. Fingers typically swell with heat, movement, or hydration changes. They’re usually largest in the evening.

Should I size up for wider bands?

Yes. Wider rings feel tighter and may require sizing up by half a size for comfort.

Are printable ring charts accurate?

Only if printed at 100% scale with no page resizing. Use them as a guide, not a final measurement.

Why does my ring feel tighter sometimes?

Temperature, swelling, and ring width can all affect how tight a ring feels. It’s normal for it to vary slightly during the day.

What ring size is 16.5mm in UK size?

Roughly a UK size L. You can check this on the ring size chart for more conversions.

How do secondhand rings differ in sizing?

They may have been resized, worn out of shape, or made to different national standards. Always check the mm measurement to be sure.

If you found this helpful, you might also enjoy this guide to hallmarking.

Final Thoughts

Ring sizing can feel more complicated than expected, but taking the time to get it right can save you the hassle of returns or adjustments. Whether you’re buying a modern stacking band or an Edwardian engagement ring, knowing your size is the first step to finding a piece you’ll love to wear.

Browse the ring collection to explore antique, vintage, and secondhand pieces available in a range of sizes.

About Ps Its Vintage

Ps Its Vintage is independently run and specialises in preloved, vintage and antique jewellery. Every piece is chosen for its character, quality and symbolism, with a focus on hallmarks, makers and meaningful design. Whether you’re choosing a stacking ring or a sentimental heirloom, this guide is here to help you choose with confidence.