# Ring Size App - Free Online Ring Sizer

*Last updated: June 03, 2026*

## Overview

Ring Size App provides a free, accurate online ring sizing tool. Use our screen calibration system and interactive ring sizer to find your exact ring size from home.

## How to Use

### Step 1: Screen Calibration

Calibrate your screen for accurate measurements:
1. Place a coin (US Quarter 24.26 mm, 1 Yuan 25.00 mm, 1 Euro 23.25 mm, Canadian 25¢ 23.88 mm, ₹5 Rupee 23.00 mm, $1 AUD 25.00 mm, or $1 SGD 24.66 mm) — or any ID-1 credit / debit card (85.60 × 53.98 mm) — flat on your screen
2. Drag the slider until the on-screen outline matches the object's edges exactly
3. The calibration is saved to your browser, so your screen stays accurate on future visits

### Step 2: Measure Your Ring Size

1. Place an existing ring that fits well on the screen
2. Drag the ring sizer circle to match the **inner diameter** of your ring
3. Read your ring size in US, UK, EU, and millimeter measurements

## Ring Size Reference

| US Size | Inner Diameter (mm) | Inner Circumference (mm) |
|---------|--------------------:|-------------------------:|
| 4       | 14.9               | 46.8                     |
| 5       | 15.7               | 49.3                     |
| 6       | 16.5               | 51.8                     |
| 7       | 17.3               | 54.4                     |
| 8       | 18.1               | 56.9                     |
| 9       | 18.9               | 59.5                     |
| 10      | 19.8               | 62.1                     |

## Tips for Accurate Measurement

- Measure at the end of the day when fingers are slightly larger
- Measure the specific finger you plan to wear the ring on
- Temperature affects finger size - avoid measuring when very hot or cold
- Wide bands require a slightly larger size than thin bands

## Related Resources

- [Ring Size Chart](/ring-size-chart) - Complete international conversion chart
- [Understanding Ring Size](/resources/understanding-ring-size) - Comprehensive sizing guide
- [Resources](/resources) - More guides and tips

## Current Region

Calibration region: **US**