Find Your Perfect Size
Accurate sizing is essential for optimal sensor performance and comfort
⚠️ Why Accurate Sizing Matters
Your OxyZen Ring must fit snugly to ensure accurate biometric readings. A ring that's too loose won't maintain consistent skin contact, while one that's too tight will be uncomfortable for 24/7 wear. Take time to measure correctly—your health data depends on it.
Two Ways to Find Your Size
Select the method that works best for you
Option 1: Measure at Home
- Instant results—order today
- No waiting for delivery
- Requires measuring tape or paper strip
- Need to be precise for accuracy
Option 2: Order Free Sizing Kit (Recommended)
- 100% accurate—try before you buy
- Test different sizes and fingers
- Completely free (shipping cost applies)
- Delivered in 3-5 business days
Measure Your Finger at Home
Follow these precise steps to measure your finger circumference accurately
Step 1: Gather Your Materials
You'll need a non-stretchable measuring tool and a ruler. The most accurate options are:
- ✓ Tailor's measuring tape (most accurate)
- ✓ Paper strip (cut to 10cm x 1cm) + ruler
- ✓ String or thread (non-elastic) + ruler
⚠️ Avoid These
Do NOT use stretchable materials like rubber bands, elastic string, or fabric tape measures. These will give inaccurate readings and result in incorrect sizing.
Step 2: Choose the Right Finger
Select which finger you'll wear your OxyZen Ring on. For optimal sensor performance, we recommend:
- 🏆 Index finger (best sensor contact)
- ✓ Middle finger (good alternative)
- ✓ Ring finger (also acceptable)
💡 Pro Tip
Most users prefer their index finger on their non-dominant hand. Measure the specific finger you plan to wear the ring on, as finger sizes vary significantly.
Step 3: Measure at the Right Time
Finger size fluctuates throughout the day due to temperature, activity, and hydration. For the most accurate measurement:
- ✓ Measure at end of the day when fingers are largest
- ✓ Ensure your hands are at normal room temperature
- ✓ Avoid measuring immediately after exercise or hot showers
- ✓ Take measurements on 2-3 different days and use the average
💡 Why This Matters
Fingers swell throughout the day and in warm conditions. Measuring when fingers are at their largest ensures your ring won't be uncomfortably tight during daily wear.
Step 4: Wrap and Measure Your Finger
Now it's time to take the actual measurement:
- Wrap the measuring tape, paper strip, or string around the base of your chosen finger (the widest part, closest to your knuckle)
- Pull snugly but not too tight—it should slide over your knuckle with slight resistance
- Make sure the material lies flat against your skin without twisting
- Mark where the end meets (for paper/string) or read the measurement directly (for measuring tape)
- If using paper/string, lay it flat against a ruler and measure in millimeters
💡 Perfect Fit Test
The correct tightness: You should be able to slide the wrapped material over your knuckle with slight resistance, but it shouldn't spin freely around your finger when at the base.
⚠️ Common Mistake
Don't measure the knuckle itself—measure the base of the finger where the ring will sit. The ring needs to fit comfortably at the base while still being able to slide over the knuckle.
Step 5: Find Your Size on the Chart
Once you have your circumference measurement in millimeters, use the size chart below to find your corresponding OxyZen Ring size.
💡 Between Sizes?
If your measurement falls between two sizes, we recommend choosing the larger size for comfort during 24/7 wear. The ring should feel snug but never tight or restrictive.
⚠️ Double-Check Your Measurement
Before ordering, measure 2-3 times on different days to ensure consistency. A 1-2mm difference in measurement can change your ring size.
OxyZen Ring Size Chart
Match your finger circumference (in millimeters) to find your perfect size
Universal Sizing Chart (All measurements in millimeters)
| OxyZen Size |
US Size |
UK/AU Size |
Circumference (mm) |
Inner Diameter (mm) |
| 6 |
6 |
L |
51.9 mm |
16.5 mm |
| 7 |
7 |
N |
54.4 mm |
17.3 mm |
| 8 |
8 |
P |
57.0 mm |
18.1 mm |
| 9 |
9 |
R |
59.5 mm |
18.9 mm |
| 10 |
10 |
T |
62.1 mm |
19.8 mm |
| 11 |
11 |
V |
64.6 mm |
20.6 mm |
| 12 |
12 |
X |
67.2 mm |
21.4 mm |
| 13 |
13 |
Z |
69.7 mm |
22.2 mm |
← Scroll to view all sizes →
💡 Sizing Tips & Recommendations
📏
Measure Correctly
Measure your finger at the end of the day when it's at its largest size. Use a proper ring sizer or printable sizing guide.
🌡️
Consider Temperature
Fingers shrink in cold weather and expand in heat. Choose a size that feels comfortable in various conditions.
💍
Snug but Comfortable
The ring should slide over your knuckle with slight resistance and sit comfortably without spinning freely.
🔄
Between Sizes?
If your measurement falls between sizes, choose the larger size for optimal comfort during 24/7 wear.
💡 How to Use This Chart
Find your measured circumference in the "Circumference (mm)" column. If your measurement falls between two sizes (e.g., 60mm), choose the larger size (Size 10 in this case) for optimal comfort.
Which Finger Should You Choose?
Optimal sensor performance depends on proper finger placement
☝️ Index Finger (Recommended)
- Best blood flow and sensor contact
- Preferred by 65% of users
- Ideal for most accurate readings
✌️ Middle Finger
- Excellent alternative with good sensor performance
- Popular choice for those who prefer traditional ring placement
💍 Ring Finger
- Acceptable for sensor accuracy
- May be preferred if you wear other rings on index/middle fingers
📌 Important Note
Avoid the thumb and pinky finger. These fingers don't provide optimal blood flow for accurate sensor readings. Most users prefer their non-dominant hand to minimize interference during daily activities.
Pro Tips for Perfect Sizing
🌡️ Temperature Matters
Fingers shrink in cold weather and swell in heat. Measure when your hands are at normal room temperature (20-22°C / 68-72°F) for the most accurate results.
💧 Stay Hydrated
Dehydration causes fingers to shrink. Ensure you're well-hydrated (but not over-hydrated) when measuring for your most typical finger size.
⏰ End of Day Measurement
Fingers are typically 5-10% larger at the end of the day. Measuring in the evening ensures your ring won't feel tight during daily wear.
📏 Measure Multiple Times
Take measurements on 2-3 different days and calculate the average. This accounts for daily variations in finger size.
🎯 Snug But Not Tight
Your ring should slide over your knuckle with slight resistance but sit comfortably at the base. It shouldn't spin freely or feel restrictive.
🔄 Between Sizes?
If your measurement falls exactly between two sizes, choose the larger size. A slightly loose ring is better than one that's too tight for 24/7 wear.
Get Your Free Sizing Kit
Not sure about measuring at home? Order our free sizing kit
Kit Features:
- 📦 Complete Size Set
- ✨ 100% Free
- 🚚 3-5 Day Delivery
- 🔄 Try Before You Buy
*Shipping cost applies: $5 domestic, $15 international
