Size Guide

Find your Halo Ring size in 2 minutes. If it doesn't fit, your first exchange is on us.

Find your size

Check the chart, calibrate your screen or enter your finger measurement.
If you're between two sizes, choose the smaller one. The ring needs a snug fit to measure accurately.
HALO size EU size Circumference Diameter
Calibrate your screen
Hold a bank card vertically over the rectangle. Drag the bottom edge until it matches exactly.
Card held vertically
54 × 85.6 mm (ISO 7810)
Drag the edge to match the card
Enter the circumference
Measure your finger's circumference with a strip of paper and a ruler in millimeters.
10
Recommended size
Size 10
Ø 19.5mm · Circ. 61.2mm

  • Free size exchange

    Your first exchange is on us. Request it within 7 days of delivery.

  • 7 sizes

    From 7 to 13, equivalent to EU ring sizes 54 to 70.

  • Real help

    Not sure? We'll measure with you. Email our team.

Three ways to measure

  • Most accurate

    With a ring you already wear

    Use a ruler to measure the inner diameter of the ring, edge to edge on the inside. Compare it with the Diameter column in the chart.

  • With paper and a ruler

    1. Cut a 1 cm strip of paper.
    2. Wrap it around the base of your finger, snug but not tight.
    3. Mark where the paper meets.
    4. Measure it in millimeters and enter it in "Your measurement".

  • On screen

    Calibrate the screen with a bank card and adjust the virtual ring until it fits your finger.

    Calibrate now

Before you measure

  • Measure at the end of the day. Fingers swell during the day and in the heat.

  • Measure the finger you'll wear it on. Each finger has a different size.

  • Account for the knuckle. The ring should slide over it with slight resistance.

  • Measure twice. If the results differ, use the average.

  • If you're between two sizes, choose the smaller one.

Where to wear it

Index, middle or ring finger of your non-dominant hand. The sensors face your palm.

For grip-heavy workouts, like pull-ups and dumbbells, switch fingers or take the ring off.

Snug, not tight.

The Halo Ring stays with you 24 hours a day, even while you sleep. The right fit is what keeps your data reliable.

  • Right

    Slides over the knuckle with slight resistance and doesn't spin on its own.

  • Loose

    Spins on the finger and the sensor loses contact. Sleep and heart rate readings fail.

  • Tight

    Leaves marks on the skin and is uncomfortable to sleep in.

Size chart

HALO size EU size Circumference Diameter
7 54 54.4 mm 17.3 mm
8 57 57 mm 18.1 mm
9 60 59.5 mm 18.9 mm
10 62 62.1 mm 19.8 mm
11 65 64.6 mm 20.6 mm
12 67 67.2 mm 21.4 mm
13 70 69.7 mm 22.2 mm

EU size is the standard ring size used by jewelers in Europe.

Going with the Halo Band? No need to measure.

The band is adjustable and fits wrists from 155 to 235 mm. Wear it on your non-dominant wrist, snug but not tight: one finger should fit between the band and your wrist.

Explore Halo Band

Frequently asked questions

What if the size doesn't fit?

Your first exchange is free. Request it within 7 days of delivery: we send the return instructions and ship the new size as soon as the ring reaches us.

I'm between two sizes. Which should I choose?

The smaller one. The Halo Ring needs a snug fit so the sensors stay in contact with your skin.

Can I use my jeweler's ring size?

Yes. Find your number in the EU size column of the chart.

Does the chart apply to Halo 2 and Halo 3?

Yes. Both models use the same size chart.

My finger changes size during the day. What now?

That's normal. Measure at the end of the day, when your finger is larger. If the ring feels a little loose in the morning, readings still work.

Can I wear the ring on a different finger?

Yes, as long as it fits snugly on the new finger. Keep the sensors facing your palm.

Does a loose ring affect the readings?

Yes. If the ring spins, the sensor loses contact with your skin and sleep and heart rate readings are incomplete.

Do I need to choose a size for the Halo Band?

No. The band is adjustable and fits wrists from 155 to 235 mm.

Still not sure?

Get in touch. We'll help you measure in a few minutes.

Contact the HALO team Buy Halo Ring