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Circul Smart Ring
Device Profile Specs

Circul Smart Ring

Compiled by Gil Sapir, Editor•Manufacturer Specifications

First smart ring that adapts to fit any finger size automatically

MSRP: $129

Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.

✓ 100% Subscription-Free ($0/mo)$$ Moderate Tier
Available Finishes:Gray
📏 Sizes M (size 7.5-9), L (13.5-18+) Available
AmazonCheck Price on Amazon

⚡ No monthly subscription fee listed

⚡

⚡ Specification Summary: Circul Smart Ring

Top RecommendationCircul Smart Ring

Circul Smart Ring offers a subscription-free hardware setup with $0 ongoing monthly software fees. Published specifications list up to 7-day battery life, Unknown, and 3g weight.

📋 Key Takeaways:

  • ✓Rated Battery Life: Up to 7 days per charge cycle (80-minute full recharge).
  • ✓Monthly Subscription: $0/month ($129.00 3-year total).
  • ✓Durability & Sizing: 5ATM / 50m water resistance with M (size 7.5-9), L (13.5-18+) sizing options.
🎯 Key Highlight

First smart ring that adapts to fit any finger size automatically

🎯 Sizing Guidance

Check manufacturer sizing guidelines prior to ordering.

Advantages & Pros

  • ✓Automatically adjusts to fit any finger size
  • ✓Tracks health metrics without the need for clinical devices
  • ✓Comfortable design for 24/7 wear

Limitations & Cons

  • ✕Battery drains quickly when using features like sleep apnea monitoring
  • ✕Customer support can be slow to respond
  • ✕Features may not work as advertised

Form Factor & Resilience

MaterialsUnknown
Width / Thickness8mm wide / 2.8mm thick
Weight3g
Water Resistance5ATM / 50m
Size RangeM (size 7.5-9), L (13.5-18+)
Sizing Kit Offered✕ No

Power Architecture

Battery LifeUp to 7 days
Charging Time minutes
Charger TypeCharging Case
Charging Case Included✓ Yes
Case Battery Capacity+7 days

Sensor Array & Biometrics

Built-in SensorsHeart Rate Monitor, Blood Oxygen Monitor, Sleep Monitor
LED Optical ColorsRed, Green, Infrared
Stress Tracking✓ Yes
Cycle Prediction✕ No
Sleep MetricsSleep Stages, Sleep Pattern Tracking

Software & Ecosystem

Companion AppCircul App
Supported OSiOS & Android
Apple Health Link✓ Yes
Google Connect Link✓ Yes
Offline StorageUp to days
Bluetooth versionBluetooth 5.0
📏 Sizing Friction Eliminator

Virtual Sizing Assistant

Convert your finger circumference to a standard US ring size. Smart ring brands may size differently from jewelers, so confirm with the manufacturer's sizing guide or sizing kit before buying.

⚠️
Swelling FactorWe recommend sizing up if your knuckles are wider than your finger base, or if you plan to wear the ring overnight (when fingers naturally swell).

Your Standard US Ring Size

US
Nearest Standard US SizeJeweler sizing, not brand-specific
8

Smart ring sizes vary by brand and model. Use this as a starting point and confirm your size with the manufacturer's sizing guide or sizing kit before ordering.

Interactive Sizing Tool

Sizing Decision Matrix (24-Hour Sizing Kit Rule)

Learn how to bypass sizing mismatches. Under the 24-Hour Sizing Kit Rule, users must wear a plastic sizing ring for a full day to capture natural biometric swelling cycles.

Video thumbnail: Official Smart Ring Sizing & Measurement Guide
Step 1 of 3

Do you own or have access to an official vendor sizing kit?

Interactive Calculator

True Cost of Ownership (TCO) Calculator

See how ongoing monthly subscription fees add up over time compared to zero-fee smart rings.

3 Years
1 Year (12 Mo)2 Years (24 Mo)3 Years (36 Mo)
Oura Ring Gen 3$514.64
$299 MSRP + $215.64 sub
Ultrahuman Ring AIR$349.00
$349 MSRP + $0 sub
Shop Oura Ring Gen 3Check Price on Amazon
Shop Ultrahuman Ring AIRCheck Price on Amazon

Cumulative Cost Projection Graph

⚠️ Critical Buyer Warning

The 2026 Smart Ring Blacklist

Common pitfalls in generic budget smart ring listings based on published specifications and public buyer reports.

01

Ring #1 to Avoid: Kuxlagz Smart Ring 2

Reason: Tiny Battery Capacity

Listed with a tiny ~20mAh battery cell, buyers frequently report short runtime between charges that makes multi-day overnight sleep tracking impractical.

02

Ring #2 to Avoid: Ti-Vision Smart Fitness Ring

Reason: Basic Sensor Hardware

Generic optical sensor module without published multi-wavelength motion compensation specs or major health-platform integrations.

03

Ring #3 to Avoid: Weyrinice Smart Ring Health Tracker

Reason: App Subscription Paywall

Places historical biometric dashboards behind a recurring companion app fee that is easy to miss on retail listings.

See the remaining 2 budget ring warnings before you buy.

Enter your email to instantly reveal the final 2 blacklisted rings.

Frequently Asked Questions: Circul Smart Ring

Does the Circul Smart Ring require a monthly subscription?

No. The Circul Smart Ring is subscription-free ($0/month), so its 3-year total cost remains equal to its $129 hardware MSRP.

How long does the Circul Smart Ring battery last?

Manufacturer specifications rate the Circul Smart Ring for up to 7 days per charge, with a full recharge time of approximately 80 minutes.

What are the Circul Smart Ring dimensions and water resistance?

The Circul Smart Ring weighs 3g, measures 8mm wide by 2.8mm thick, is constructed from Unknown, and is rated for 5ATM / 50m.

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