Ring Size Guide — How to Measure Your Ring Size

Your ring size is determined by measuring your finger in millimetres. You can find it at home with a strip of paper and a ruler, but for a ring you'll wear every day, confirm with a physical sizer and, if it's an engagement ring, a replica before the final piece is crafted. IRALIS sends a free ring sizer to your door and offers personal sizing guidance as part of every consultation.

How Do I Measure My Ring Size at Home?

Your ring size comes down to one measurement: how big around your finger is, in millimetres. In Switzerland and the EU, the size number equals the inner circumference. A size 52 means 52mm around the inside of the ring, which works out to about 16.5mm across (the diameter). US and UK systems use their own scales, but millimetres are the universal starting point.

Here's the most reliable method using materials you already have.

What you need: A strip of paper or non-stretch string, a pen, and a ruler with millimetre markings.

Step 1. Wrap the strip snugly around the base of your finger. It should pass over your knuckle without forcing. Not tight, not loose.

Step 2. Mark where the strip overlaps with the pen.

Step 3. Lay the strip flat against the ruler and read the length in millimetres. This is your circumference.

Step 4. Divide by 3.14 to get the diameter. Example: 52mm circumference ÷ 3.14 = 16.6mm diameter.

Step 5. Match your diameter to the size chart below.

A few things affect accuracy. Measure at the end of the day, when your fingers are at their largest. Room temperature is ideal. Cold hands shrink, warm hands swell. And if you're between marks, round up rather than down.

For the most dependable result, request a free IRALIS ring sizer. It's a professional-grade gauge mailed directly to you, calibrated for Swiss sizing, and more accurate than paper or string.

What Ring Size Am I? Ring Size Chart

The chart below converts between Swiss/EU, US, and UK systems. Swiss ring size equals the inner circumference in millimetres.

Most women wear between size 48 and 56, with 52–54 being the most common. Most men wear between 57 and 62.

If you're converting from a US or UK size, use this table rather than online calculators. Rounding errors compound quickly, especially near half-sizes.

How Do I Find Out My Partner's Ring Size Secretly?

The most reliable method is borrowing a ring your partner already wears on the correct finger. Place it flat on paper, trace the inside circle, and measure the diameter. Even a ring from the opposite hand gives a close starting point.

Other approaches that work:

• Ask a close friend or family member. They may already know, or they can ask without raising suspicion.
• Check their jewelry box. A ring from the right hand is typically one size larger than the left ring finger.

If none of these feel reliable, you're not stuck. IRALIS offers a replica ring service for exactly this situation. A replica of the engagement ring is made to the estimated size, so your partner can try the design and fit before the final piece is crafted in precious metal and stones. No guesswork. No pressure to get it right on the first try.

What If I'm Between Two Ring Sizes?

For narrow bands (under 3mm), go with the smaller size. Slim rings have less surface contact, so they naturally fit a little looser.

For wider bands (3–5mm), go up a half size. The extra width creates more friction against your skin. A ring that fits well in a slim band will feel tighter in a wider design.

For bands 6mm or wider, go up a full size.

When you're genuinely caught between two sizes and can't decide, go larger. It's easier to size down slightly than up, so rounding up gives you more flexibility.

This is also where a conversation makes the difference. IRALIS's team sizes every ring individually, factoring in band width, setting style, and how you wear your jewelry. A ten-minute consultation narrows the decision faster than any chart.

How Does Ring Width Affect Ring Size?

Width matters more than most guides acknowledge. A 2mm solitaire band and a 6mm eternity ring with the same inner diameter will not feel the same on your finger.

Here's the rule:

• Under 3mm (most solitaire bands, thin stacking rings): true to size.
• 3–5mm (standard wedding bands, pavé bands, halo settings): consider going up half a size.
• 6mm and wider (bold statement rings, wide eternity bands): go up a full size.

The reason is contact area. Wider bands press against more skin, making the ring harder to slide over your knuckle. The inner diameter hasn't changed, but the fit has. 

If you're choosing between designs with different widths, ask about sizing for each. A single size doesn't always cover both.

Does Ring Size Change Over Time?

Yes. Your fingers fluctuate throughout the day and across seasons. They're smallest in the morning and in cold weather, largest in the evening and in heat.

Other factors: pregnancy and hormonal changes can increase ring size by one to two sizes temporarily. Weight fluctuations affect finger size gradually. Even altitude and salt intake have a short-term effect.

Practical guidance: measure at the end of the day, at room temperature, when you haven't just exercised. That gives you the most representative size. If you know you tend to retain water, measure on a few different days and take the most common result.

What Happens If I Order the Wrong Size for a Custom Ring?

With made-to-order jewelry, sizing is built into the production process, not patched after the fact. Your ring is crafted to the confirmed size from the start. That's why IRALIS uses a three-step sizing protocol: self-measurement, confirmation with a physical ring sizer, and for engagement rings, a replica to try before the final piece is made. Every ring is sized individually based on your finger profile, your chosen design, and the width of the band. The protocol catches sizing questions before production begins.

For engagement ring buyers, the replica service lets you confirm both design and fit on your hand before the final piece is crafted. Lead times for replicas run up to 10 weeks, so starting the conversation early gives you the most flexibility.

And if your size changes after delivery, IRALIS offers free resizing up to two sizes in either direction for all rings that are not eternity bands. Life changes, weight shifts, seasons affect your hands. Your ring should still fit.

The one exception: eternity bands, where lab-grown diamonds are set around the full circumference, cannot be resized without altering the design. For eternity rings specifically, the sizing protocol matters most. Getting it right before crafting is the only path.

Your IRALIS consultant walks through all of this before production begins, so there are no surprises.

Your Next Step

Request your free IRALIS ring sizer, or book a personal consultation with the team. Whether you're choosing your own piece or planning a surprise, you'll have expert sizing guidance before anything is crafted.

→ Request your free ring sizer → Book a consultation