Scale a pattern measurement up or down.
Scale every measurement by the same percentage to keep proportions.
Scaling a pattern changes all its measurements by the same percentage. Divide the new size by the original size and multiply by 100 to find the scale, so an 8 inch piece enlarged to 10 inches is scaled to 125 percent. Enter an original measurement and the scale percentage to see the new measurement.
This works well for crafts such as toys, bags, appliqué shapes, and quilt blocks, where every part can grow or shrink together. It does not work well for fitted clothing, since bodies do not change proportion evenly with size. Garment sizes are graded with different changes for different measurements.
Remember that seam allowances are part of the pattern. If a pattern includes them, they will scale along with everything else, so it is usually better to scale the finished size and then add the seam allowance back. Print or photocopy at the exact percentage and check one measurement against a ruler.
Make a test version in inexpensive fabric before you cut the final piece, and be sure the thread, trims, and notions are scaled to match, since a large pattern may need heavier materials and a small one finer ones.