Enlarging pattern
 

I'm hoping someone can help me. I have found a quilt pattern I want to make that is about 57 inches square but I need it to be 90 inches square to fit my bed. It has one large central motif of approximately 18.5 inches which is surrounded by 6 borders each containing different smaller motifs. To get the required finished size I am thinking I will repeat 4 of the borders. My quandary is how I go about calculating the extra fabric I am going to need for each of the extra borders and their motifs. How do I go about this?

If you have a fabric calculator, you can use that to calculate how much you need. If you have an EQ program, you can use it to sketch out the quilt and the program will tell you the amounts of each fabric you need. Otherwise, you may have to estimate by studying the pattern and the amounts of the different fabrics which are required for the borders you want to repeat. Remember that each subsequent border will be larger than the one before it, so it's not just a matter of doubling those amounts. The longer borders will require more fabric than the original ones.

If I understand correctly, you want to enlarge a medallion quilt. The original design has a center medallion 18.5" square and 6 pieced borders bringing the total size to 57" square. The problem is that unless we know exactly what designs the pieced borders use, what colors are dominant etc., we can't provide a very accurate estimate. However, mathematically we can get a swag:
Original quilt is 57X57 or 3249 square inches. The medallion is 342 square inches so the borders are about 2907 square inches.
Target quilt is 90X90 or 8100 square inches. Same medallion, so the borders are about 7758 square inches, which is about 2.66 times the original border area. You could take the original fabric requirements and multiply them by 2.66. Personally, I'd get 3X the original amounts. Which is why my scraps & stash piles look like they do!
The only way to get an accurate estimate is to figure out how many squares, HST, etc. for each block in each border, how many of those you can get out of a yard/meter of fabric, and how many you need for your new design...

This is the main reason I have Electric Quilt. You can put the pattern the size it is and then by a click of a mouse enlarge it until you get the size you want. I would suggest you draw out the pattern on gridded graph paper and then stat making the change of size of each of the blocks but increase the size of the grid.

Extra borders are fairly easy to figure out. This is how I do it. When I buy fabric I add several extra inches in case I have to square the fabric back up again.

Right now your quilt is 57" square. Let's add the first border...a 3" one. You need to know how many inches of fabric you will need. So the first two sides will be 57 each. The next 2 will be 57+3 = 60". So you have 57 + 57+ 60+ 60 = 234" total. Now if your fabric is 40" wide, divide the border inches by 40" = 5.85 strips, round up to 6. I didn't allow for seams, so probably add 1 more strip to be 7. Now multiply the 3" width by 7 = 21" of 40" wide fabric.

Now, go back to finding what your next border inches will be. Let's do a 4" wide. 60 + 60 +64 +64 = 248 inches. Divide 248 by 40" width of fabric = 6.2 widths x 4 inch wide cuts = 24.8 inches of 40" wide fabric.

And yes....I did love math in school, but that was a long time ago these days.

Thankyou so much everyone..I really appreciate the advice and now feel I can have a go at doing the estimates. Thankyou again for pointing me in the right direction and not making me feel stupid!

I agree with ManiacQuilter2. If you don't have EQ, maybe a friend does and would be willing to help you out. I've helped many friends using my EQ.

Extra borders might not have the impact you want.

I am thinking that the center medallion would look very "small" in the center of the enlarged quilt.

Perhaps enlarge everything by the same ratio?

There fabric calculators on the web free..but when I do something like that..I increase the material the pattern calls for by how many extra rows..if say the blue color for the border for 3 rows is one yard..and I want 3 more border rows just like the pattern roll..I buy another yard..I am one of these people who hardly ever finish a pattern the way it is lay out..I usually always go bigger..or if I am not completely sure..I buy more..I love scrape quilts so this works for me...

https://ankastreasures.files.wordpre...c_8111-adj.jpg

I hope this link works. It is Heather mulder petersen's blog, October 2013. Someone posted this picture here not too long ago and I had an ah ha moment. Why not do as Heather does and layer smaller pieced quilt (60+") on a solid quilt. I'd I were you, I'd leave the size it is.