Bag Calculator
Estimate how much fabric you need for a tote bag or similar project, and see the box corner size if you are sewing a structured bag.
This follows the Omni formula: width and height are based on the bag dimensions plus a fixed seam allowance, and the box corner is half the depth.
Fabric Estimate
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Run the calculation to see the fabric and box corner measurements.
Quick Answer
The bag calculator estimates the cut size of the fabric and the size of the box corners from your desired bag width, height, and depth.
How to Use It
- Enter the desired width, height, and depth of the bag.
- Choose inches or centimeters.
- Click Calculate.
- Use the fabric dimensions as your cutting guide.
Formula
Fabric width = 2 × width + 2 × depth + 1
Fabric height = height + depth / 2 + 1
Box corner = depth / 2
The fixed 1-inch extra length represents the seam allowance from the reference formula.
Worked Examples
Example 1: A 32 x 44 x 18 inch bag needs 102.5 x 55.5 inches of fabric and 9 inch box corners.
Example 2: A 40 x 30 x 10 cm bag can be converted into inches before using the formula.
Example 3: A deeper bag always increases the box corner size because it is half the depth.
How to Interpret the Result
| Output | Meaning |
|---|---|
| Fabric width | The cut width needed for the main panel. |
| Fabric height | The cut height needed for the main panel. |
| Box corner | The square cutout size needed to create a boxed bottom. |
Frequently Asked Questions
Related Calculators
References
- OmniCalculator reference page
- The formula uses the width, height, depth, and a fixed seam allowance from the reference page.
- Last reviewed: March 2026.