A diamond’s length to width ratio signifies how proportionate the diamond is with its intended shape (i.e. square vs. rectangular) and is determined by dividing the diamond’s length by width. As an example, if a diamond’s length measures 5mm and its width is 3.5mm, the length to width ratio is 1.43.
The ratio you choose for your radiant diamond is entirely dependent on what you find to be the most aesthetically pleasing. A common range for radiant length to width ratios is 1.00-1.35, with the lower end indicating a more square shape. Length to width ratios can go up to 2.0 for a more rectangular shape.