Ring Size Guide

The most reliable way to determine ring size is to have a jeweler measure the intended finger with a properly calibrated set of sizing rings. At-home measurements are estimates and should be checked before ordering, especially for pavé, eternity, unusually wide or custom designs.

Important: Do not rely on string or a strip of paper as the only measurement. String can stretch, paper can bend or change with humidity, and neither method properly accounts for the knuckle.

Method 1: professional finger sizing

Ask a local jeweler to measure the exact finger and hand on which the ring will be worn. A ring should pass over the knuckle with slight resistance and then sit comfortably without feeling tight or turning freely.

  • Use a narrow sizing gauge for a narrow band and a wide sizing gauge for a band wider than approximately 4 mm.
  • Tell the jeweler if the engagement ring will be worn next to a wedding band; the combined width can change the fit.
  • Measure more than once if your hands are unusually warm, cold or swollen.
  • Record the US size and the intended finger and hand.

Method 2: measure a ring that already fits

Use a plain, round ring that fits the same finger and hand. This method is less reliable if the reference ring is bent, oval, very wide, open at the back or has an unusual interior profile.

  1. Place the ring flat on a stable surface.
  2. Use a millimetre ruler or caliper to measure straight across the widest part of the opening, from one inside edge to the opposite inside edge.
  3. Do not include the metal in the measurement.
  4. Repeat the measurement in two directions. If the results differ, the ring may not be perfectly round and should be checked by a jeweler.
  5. Match the inside diameter to the chart below.

Method 3: use a physical ring sizer

If an in-person measurement is not possible, use a reusable plastic or metal ring-sizer set that shows US whole and half sizes. Follow the maker’s instructions, test adjacent sizes and make sure the selected size passes the knuckle without excessive force. A physical sizing ring is generally more dependable than a printed line or a paper strip.

Before you decide

  • Measure the correct finger and hand. Fingers on opposite hands can differ.
  • Check the knuckle. The ring must pass over it and still sit securely at the base of the finger.
  • Avoid extremes. Cold can make fingers feel smaller; heat, exercise, travel and fluid retention can make them feel larger.
  • Consider band width. Wide bands and stacked rings often feel tighter than narrow bands of the same marked size.
  • Consider the design. Full-eternity, extensive pavé and some custom rings can be difficult or impossible to resize.
  • Do not guess from averages. Height, weight or another person’s size cannot determine the correct fit.

US ring size conversion chart

The values below are a comparison guide derived from GIA’s international ring-size chart. Manufacturing tolerances and conversion tables can differ slightly. A calibrated sizing gauge remains the preferred method.

US ring sizes 3–12: inside diameter and circumference
US size Inside diameter Inside circumference
3 14.1 mm 44.3 mm
3.5 14.5 mm 45.6 mm
4 14.9 mm 46.8 mm
4.5 15.3 mm 48.1 mm
5 15.7 mm 49.3 mm
5.5 16.1 mm 50.6 mm
6 16.5 mm 51.8 mm
6.5 16.9 mm 53.1 mm
7 17.3 mm 54.3 mm
7.5 17.7 mm 55.6 mm
8 18.1 mm 56.9 mm
8.5 18.5 mm 58.1 mm
9 19.0 mm 59.7 mm
9.5 19.4 mm 60.9 mm
10 19.8 mm 62.2 mm
10.5 20.2 mm 63.5 mm
11 20.6 mm 64.7 mm
11.5 21.0 mm 66.0 mm
12 21.4 mm 67.2 mm

How a correctly fitted ring should feel

The ring should move over the knuckle with gentle resistance, sit comfortably at the base of the finger and remain secure during normal movement. It should not cause pain, numbness or a deep indentation. If the ring spins constantly or can slide off without resistance, the fit may be too loose.

Resizing and design limitations

AIMINIA currently offers one standard resizing within 90 days of delivery when the design can be safely resized. Eternity bands, extensive pavé settings and certain custom designs may not be resizable. Eligibility is confirmed after inspection; review the full Limited Lifetime Craftsmanship Warranty and resizing terms before ordering.

If you are between sizes or the design is wide or difficult to resize, email hello@aiminiajewelry.com with the ring name, intended finger and the measurements you obtained before placing the order.

Frequently asked questions

Should I choose the larger size when I am between sizes?

Do not apply one rule to every design. Band width, knuckle size and setting style can change the correct choice. Ask a jeweler to verify the fit or contact AIMINIA with the product name before ordering.

Can I measure with string or paper?

Those methods can produce inaccurate results because the material may stretch, bend or fail to account for the knuckle. Use a professional sizing gauge, a physical ring sizer or the inside diameter of a correctly fitting round ring instead.

Does a wide ring use the same size?

A wide band often feels tighter than a narrow band with the same marked size. GIA recommends using wide-finger sizing gauges for rings wider than approximately 4 mm.

Can every AIMINIA ring be resized?

No. Eternity, extensive pavé and certain custom designs may have limited or no resizing range. Eligibility depends on the design and condition and is confirmed after inspection.

Why does my finger size change?

Temperature, humidity, activity, travel and normal swelling can change how a ring fits. Measure under comfortable, typical conditions and repeat the check.

Sources and methodology

Last reviewed: August 19, 2026. This guide provides general sizing information and does not replace an in-person fitting.