I know that mitered borders scare a lot of people but they're really not that hard. I'll be the first to admit they scared me at first. Once you know a couple of little tricks, they're really not that difficult. Just take your time with them and it'll all work out, I promise!
Mitered corners look beautiful even with just one border. Admittedly, this one doesn’t show up very much because the print is a little bit busy. You can see there's a really nice point on that mitered corner. Everything meets up. There are no dimples, no lumps, no bumps.
This technique also looks stunning with multiple borders or stripes. Maybe you have a couple of colors that you want to put together.
Miter Border Formula
Basic One Color Border
First thing, you need to know is how long to cut the borders. You will need extra fabric on the ends so that you can actually turn and stitch that miter.
Measure the length of your project, let’s say it’s a quilt, then add double the width of the border. Add 2 to 4 inches to that number for wiggle room. Let’s say the project is 24 inches long and the border is 3 inches wide. Your length-wise border should be 32 to 34 inches long [24 (length) + 6 (border is 3 inches wide x 2 = 6) + 2 to 4 (wiggle room) = 32 to 34 inches].
The width measurement is determined the same way. Take the width of the quilted piece add to that the width of the border times two, plus 2 to 4 inches for wiggle room. If your item is 12 inches wide with a 3-inch wide border, your width-wise borders should be 20 to 22 inches long.
Use the same formula for double borders. Make your border strip set first and use the same length and width formula that I just described. Measure the length of the piece, add your total border strip set width times two, and then 2 to 4 inches extra for wiggle room.
Before adding borders, make sure the quilt is properly squared up. You want to have nice 90-degree corners.
Find the middle of your border and mark it with a pin. Find the middle point of the quilt edge and put a pin there. Match up center pins and smooth everything flat, right sides together. Pin the border to the quilt on a flat surface. No lumps and bumps or puckers. Measure in 1/4 of an inch from the corner edge of the quilt and make a little mark right on the border. I'm going to the other side and do the very same thing.
I sewed exactly from that quarter-inch mark all the way to the other end and I stopped exactly at that quarter-inch mark. This is very important. You don't want to stitch past that quarter-inch mark because you might get a dimple.
I set my stitch length to 2.0. I shortened it up just a little bit as it makes the seam stronger plus it's easier to start and stop exactly where you want. Stitch top and bottom borders to the quilt, stopping a quarter inch inside the edges of the quilt. Press seams away from the quilt.
Sewing Mitered Borders
Here's where it all comes together! Fold your quilt in half on the diagonal on a large flat surface, right sides together. You want everything to be nice and flat making certain the raw edges of your border match up, that's the most important thing. Pin together.
Take your ruler and put the 45-degree angle from your ruler right on the stitching line. The edge of the ruler should be right at that start and stop point of your stitching. Draw a 45-degree angle right across the border fabric starting at the ending point of previously stitched seam.
The newly drawn line starts at end of stitching, and it goes out 45 degrees across border to raw edge. Make sure the seam allowances are out of the way and pressed toward the quilt.
Drop the needle right through the starting point and stitch down the center of drawn line on border and sew.
Take out the pins, open it up. It looks really good, if I may say so myself.
If everything looks okay, take your little ruler and your rotary cutter and trim with a quarter-inch seam allowance.
Press the seam on the mitered corner open. Press the seam where the quilt meets your border toward the border.
Mitering Striped Borders
Identical stripes are mitered the same way as prints.
If it's not an even stripe, such as two little stripes and then a big fat stripe and two little stripes and a big fat stripe, some modification is needed. Determine how wide you want the border and cut the same stripe sequence for each border. Cut a single layer of fabric at a time to be sure your striped borders are all cut the same.
On that predominant stripe, you would take a pin or a wonder clip and mark the top of your stripe. That will keep your stripes lined up and going the same direction.
Get the video tutorial here.