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The Lightbox Team
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Shipping & Returns
Shipping
We offer two secure shipping options via Fedex, standard and overnight expedited. Shipping methods and prices will be shown in check-out based on your shipping address and order value.
We do not ship to U.S. P.O. Boxes; U.S. territories; and APO/FPO/DPO addresses.
Please note, we require a signature upon delivery.
Orders received before 2pm EST Monday-Friday will be dispatched same day. Orders received after 2pm will be dispatched next business day.
Returns
All orders placed from July 1, 2025 are final and are not eligible for returns or exchanges.
We are happy to offer free returns and exchanges within 30 days of the date your package was delivered. Your original shipping charge is non-refundable but return shipping is free.
Read our complete shipping and returns policy >
Ring Size Guide
Compare your finger measurement to the chart below and choose your corresponding ring size.
Size Conversion Chart
|
US |
UK |
Europe |
Inside circumference (mm) |
Inside circumference (inches) |
| 5 | J | 48.5 | 49.3 | 1.94 |
| 5.5 | K | 50 | 50.6 | 1.99 |
| 6 | L | 51 | 51.9 | 2.04 |
| 6.5 | M | 52 | 53.1 | 2.09 |
| 7 | N | 55 | 54.4 | 2.14 |
| 7.7 | O | 56 | 55.7 | 2.19 |
| 8 | P | 57 | 57.0 | 2.24 |
| 8.5 | Q | 58.5 | 58.3 | 2.29 |
| 9 | R | 59 | 59.3 | 2.34 |
Check the size of your existing ring
Print or download our ring size guide and follow instructions to find out what size your existing ring is. Please note: This is a printable desktop download. If you are viewing on a mobile screen, the ring sizer will appear smaller and give an inaccurate measurement.
Helpful Hints
- Our dominant hands are generally slightly larger — make sure you measure the right finger on the correct hand!
- Rings with wider bands will fit a bit tighter. If you plan to measure one of your rings, try to measure one with a similar width as the ring you want to purchase.
- Make sure the finger is at normal body temperature — fingers can shrink or expand when hot or cold.
- Your fingers tend to change size throughout the day — the best time to measure your finger is at the end of the day.
- If your knuckle is bigger, take 2 measurements and choose a size in between — rings need to fit over the knuckle but not be too loose or it will shift around.
Guide
The total weight of our products may vary, so please see the table below for more information about the carat weights we offer on stones:
Round Brilliant Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Diameter Girdle (approx. min. in mm) | Diameter Girdle (approx. max. in mm) |
| ½ | 0.47 | 0.52 | 5.0 | 5.3 |
| ¾ | 0.71 | 0.78 | 5.6 | 6.0 |
| 1 | 0.95 | 1.05 | 6.2 | 6.6 |
| 1½ | 1.46 | 1.57 | 7.1 | 7.5 |
| 1¾ | 1.70 | 1.83 | 7.5 | 7.9 |
| 2 | 1.95 | 2.10 | 7.9 | 8.3 |
| 2¼ | 2.20 | 2.36 | 8.3 | 8.7 |
| 2½ | 2.45 | 2.62 | 8.5 | 8.9 |
| 3 | 2.95 | 3.15 | 9.2 | 9.6 |
Princess Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. min. in mm) | Length (approx. max. in mm) |
| ½ | 0.47 | 0.52 | 4.1 | 4.3 |
| ⁵⁄₉ | 0.52 | 0.57 | 4.3 | 4.5 |
| ⅝ | 0.59 | 0.65 | 4.5 | 4.7 |
| ¾ | 0.71 | 0.78 | 4.8 | 5.0 |
| ⅞ | 0.83 | 0.91 | 5.0 | 5.2 |
| 1 | 0.95 | 1.05 | 5.3 | 5.5 |
| 1½ | 1.46 | 1.57 | 6.1 | 6.4 |
| 1¾ | 1.70 | 1.83 | 6.4 | 6.7 |
| 2 | 1.95 | 2.10 | 6.6 | 7.0 |
| 2¼ | 2.20 | 2.36 | 6.9 | 7.3 |
| 2½ | 2.45 | 2.62 | 7.1 | 7.5 |
| 2¾ | 2.70 | 2.88 | 7.4 | 7.8 |
| 3 | 2.95 | 3.15 | 7.6 | 8.0 |
Cushion Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. min. in mm) | Length (approx. max. in mm) |
| ½ | 0.47 | 0.52 | 4.3 | 4.5 |
| ⅝ | 0.59 | 0.66 | 4.6 | 4.8 |
| ¾ | 0.71 | 0.78 | 4.9 | 5.1 |
| ⅞ | 0.83 | 0.92 | 5.2 | 5.4 |
| 1 | 0.95 | 1.05 | 5.4 | 5.6 |
| 1½ | 1.47 | 1.57 | 6.3 | 6.7 |
| 1¾ | 1.72 | 1.83 | 6.6 | 7.0 |
| 2 | 1.95 | 2.10 | 6.9 | 7.3 |
| 2¼ | 2.20 | 2.36 | 7.2 | 7.6 |
| 2½ | 2.45 | 2.62 | 7.3 | 7.7 |
| 2¾ | 2.70 | 2.88 | 7.6 | 8.0 |
| 3 | 2.95 | 3.15 | 7.8 | 8.2 |
Emerald Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. mm) | Width (approx. mm) |
| 1 | 0.95 | 1.05 | 6.6 | 4.7 |
| 1½ | 1.46 | 1.57 | 7.6 | 5.4 |
| 1¾ | 1.70 | 1.83 | 8.0 | 5.7 |
| 2 | 1.95 | 2.10 | 8.3 | 6.0 |
| 2¼ | 2.20 | 2.36 | 8.7 | 6.3 |
| 2½ | 2.45 | 2.62 | 9.0 | 6.4 |
Oval Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. mm) | Width (approx. mm) |
| 1 | 0.95 | 1.05 | 7.8 | 5.6 |
| 1½ | 1.46 | 1.57 | 8.9 | 6.4 |
| 1¾ | 1.70 | 1.83 | 9.3 | 6.8 |
| 2 | 1.95 | 2.10 | 9.6 | 7.0 |
Asscher Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. min. in mm) | Width (approx. max. in mm) |
| 1½ | 1.46 | 1.57 | 6.0 | 6.4 |
| 1¾ | 1.70 | 1.83 | 6.4 | 6.8 |
| 2 | 1.95 | 2.10 | 6.8 | 7.2 |
| 2¼ | 2.20 | 2.36 | 7.0 | 7.4 |
| 2½ | 2.45 | 2.62 | 7.2 | 7.6 |
| 2¾ | 2.70 | 2.88 | 7.4 | 7.8 |
| 3 | 2.95 | 3.15 | 7.7 | 8.1 |
Baguette Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. mm) | Width (approx. mm) |
| ¼ | 0.24 | 0.26 | 4.30 | 2.90 |
| ½ | 0.48 | 0.53 | 5.34 | 5.56 |
Trillion Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. mm) | Width (approx. mm) |
| ¼ | 0.24 | 0.26 | 4.50 | 4.50 |
Heart Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. mm) | Width (approx. mm) |
| ¼ | 0.23 | 0.27 | 4.0 | 4.4 |
Pear Cut Stones
| Carat Weight | Min Carat Weight | Max Carat Weight | Length (approx. mm) | Width (approx. mm) |
| ¼ | 0.25 | 0.27 | 5.1 | 3.5 |
Quality Guaranteed
Our stones are made to a consistently high standard and are inscribed with a mark of quality invisible to the naked eye. For full details on our stone grading, visit our quality verification page >
Please note: Pink and blue stones, and stones above 1 carat in size are subject to a post-growth enhancement.
Seal of Authenticity
Laser-inscribed on every Lightbox lab-grown diamond, and invisible to the naked eye.
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Grown with 100% renewable energy
All our diamonds are grown in the USA with 100% wind power, using some of the most advanced technology in the industry.
Read more about our approach to sustainability >