It is easy to change the size of most quilt blocks once you understand patchwork quilt block structure. Examine quilt structure before you get started.
Popular quilt block layouts:
- Four-patch quilt block: These are made up of four square grids—two across and two down.
- Nine-patch quilt block: These are made up of nine-square grids—three across and three down.
- Five-patch: These describe how many square grids exist in a single row across or down, not the total number of grids in the quilt block.
Four-patch and nine-patch quilt blocks are routinely subdivided to create more intricate patterns, but once you become a block watcher it will be easy to identify their underlying structure.
Five-patch and seven-patch block grids can be subdivided into multiple patch units, but that is not quite as common, other than the use of half-square triangles because the grids are usually a bit small already. Individual grids in a quilt block are sometimes combined, rather than subdivided, like the areas created by red strips in the five-patch block.
Why Block Structure Matters
Once you can decipher a quilt block's grids, you can make it larger or smaller with ease. And although the structure is important for altering the size of a quilt block, it is also a huge component when designing a quilt, because some blocks just do not mesh when sewn side-by-side, even if they are the same size. It is very important to always make a test block in the new size before cutting all of your fabric.
Different Methods for Size Alterations
Some quilt blocks are easier to scale using different techniques. An eight-pointed star made with diamonds (versus the cheater version with half-square triangle units) and blocks with curved patches (which are sometimes more difficult to draw correctly) are two examples.
If you find a block that is not easy to alter, make a photocopy, enlarging or reducing the block to the finished size you wish to sew. Measure the sizes of its patches (remembering that the dimensions are unfinished). Use templates to construct the block or refer to patchwork shape cutting instructions to choose a patch and block size that can be easily rotary cut. All shape sizes must be altered in the same way.
Patchwork quilt blocks and other quilt components are typically sewn together using a 1/4-inch seam allowance. Some people may assemble miniature quilts with a 1/8-inch seam, but this is not recommended.
Foundation-pieced blocks (sometimes called paper pieced blocks) are not sewn with precise seams allowances).
Patterns nearly always list sizes you must cut, and they do not give finished sizes. If you get a pattern giving finished sizes in cutting instructions, then steer clear of the pattern, unless it is for applique.
For patchwork with straight sides of 90-degree angles from each other, such as squares, rectangles, and bars, you will add 1/4 inch to each unfinished dimension to determine the correct cutting (unfinished) size for a total of 1/2 inch to the length and width.
- A 3-inch by 3-inch finished square would be cut 3 1/2 inches by 3 1/2 inches
- A 2-inch by 4-inch finished rectangle would be cut 2 1/2 inches by 4 1/2 inches
The amount added to the finished sizes of patchwork pieces with angled edges, such as triangles and diamonds, varies depending on the shape, but you will still sew these pieces to neighboring patches with a 1/4-inch seam allowance.
Scaling Quilt Blocks Up or Down
It is easy to change a patchwork quilt block's finished size by altering the size of each grid in the block. Finished sizes of block grids do not need to be in whole numbers. Use fractions if preferred, as long as they are dimensions you can cut with a rotary cutter (if not, plan to construct your block with templates).
When considering block size, determine finished sizes first.
The most simple quilt block to scale up or down is a block made up of only squares of fabric. For a nine-patch block, any finished block size will work as long as it is divisible by three. Finished sizes that are possible include:
- 15-inch block: Nine squares that finish at 5 inches by 5 inches each
- 12-inch block: Nine squares that finish at 4 inches by 4 inches each
- 9-inch block: Nine squares that finish at 3 inches by 3 inches each
- 7-1/2-inch block: Nine squares that finish at 2 1/2 inches by 2 1/2 inches each
- 6-inch block: Nine squares that finish at 2 inches by 2 inches each
Notice that squares do not have to finish in even numbers. Any number that is rotary cuttable will work just fine.
Changing the Size of More Fussy Quilt Blocks
There may be times you choose to make quilt blocks only from squares, but most of your blocks will be a bit more intricate, and sizing them up or down will require a few extra considerations.
For example, the nine-patch block is made up of nine grids, but only two of those grids are simple squares. Four are half-square triangle units and three are smaller nine-patch units.
Always consider the grids containing the smallest patches when you choose a finished block size.
Making a 15-inch Block to Rotary Cut
The grids that hold small nine-patches would finish at 5 inches square. Dividing 5 inches (the grid size) by 3 (the number of squares across and down in the small units) equals 1.66 inch, a dimension that cannot be cut accurately with a rotary ruler.
Instead, make a quilt block that finishes at about 15 inches. Use 1 3/4-inch (finished) squares in those units instead of the 1.66 inches required for a 15-inch block. The result (1 3/4 inches by 3 inches) would produce a 5 1/4-inch (finished) grid.
Multiply 5 1/4 by 3 (to account for all grids in the block, which must be equal), and you will have quilt blocks that finish at 15 3/4 inches, a perfectly acceptable size unless the blocks must match their 15-inch neighbors.
Cutting Patchwork for a 15 3/4-Inch Finished Block
Determine your design and cut accordingly.
- Four half-square triangle units: Cut two 6 1/8 inches by 6 1/8 inches dark squares and the same number and size of light squares. Cut in half once diagonally and sew contrasting squares together on their longest edges. Or leave the squares as is and use a quick piecing method to sew the units.
- Two large squares: Cut two 5 3/4-inch by 5 3/4-inch squares.
- Three small nine-patch units: Cut (15) 2 1/4-inch by 2 1/4-inch dark squares and (12) 2 1/4-inch by 2 1/4-inch light squares (assuming you will not strip piece the small nine patch units).
Altering the Size of Four-Patch Quilt Blocks
Four-patch quilt blocks have four primary grids, but the majority of blocks you will encounter have been divided again to create an eight-grid structure. You already know how to enlarge or reduce a quilt block made with only squares of fabric, and changing the size of a more complex block is accomplished with the same methods we used for the nine-patch block.
Sawtooth Star With 16-Patch Center
The sawtooth star quilt block shows the design's four-patch grid, and it is easy to visualize dividing the grids again horizontally and vertically, placing the star tips, block corners, and four small squares into grids of their own (four grids across and four down). Another variation is the evening star with nine-patch center.
Here's how to make the sawtooth star block in a 12-inch finished size:
Examine the smallest patches of the grids first which are the little squares at the block's center. If you visualize the divided grid arrangement, you can see there are two small squares in each grid.
- 12 inches divided by 4 is 3 inches (finished) for each of the grids
- 3 inches divided by 2 is 1 1/2 inches (finished) for each of the two small squares in a grid, a size that is rotary cuttable; if a finished size is rotary cuttable, the patch will still be rotary cuttable after adding the seam allowance
Here's how to make the sawtooth star block in a 10-inch finished size:
The half square triangle units and plain corner squares are doable for any rotary cuttable size, so a 10-inch block is a valid choice.
- 10 inches divided by 4 is 2 1/2 inches (finished) for each of the grids
- 2 1/2 inches divided by 2 is 1 1/4 (finished) for each of the small squares
Bonnie Scotsman Quilt Block
Bonnie Scotsman quilt block can be assembled in a couple of ways. You can make units that look just like the four grids, but the block's patchwork will flow a bit better if you extend the long, light bars on the top and right edges to touch the dark corner square, rather than piecing them separately to create a four-patch unit.
The grid not only helps you calculate sizes, but it also allows you to diagnose the block's structure. A huge percentage of quilt blocks can be assembled in multiple ways, and examining grids lets you begin exploring the options.
Take a look at the sew and slice Bonnie Scotsman pattern for an even easier way to sew the blocks.
More Intricate Quilt Structure and Final Tips
Sometimes a quilt block's type or grid structure is not immediately apparent. It takes some practice.
- Greek cross: This block is one of many blocks with an unequal design. It could be made into a five-patch block if the narrow inner bar areas were exactly half the width of the outer half-square triangle corners, but many versions use narrower bars in those center slots.
- Swamp angel: This has lots of angled patchwork, but look at it closely and you will see that it is a pretty simple nine-patch arrangement.
- Arizona quilt block: This is another nine-patch quilt block with grids that have been subdivided.
- Five-patch chain: This is a five-patch block with some subdivided grids.