How do I adjust a woodworking plan's dimensions to fit my room?

Start by changing the one dimension that has to fit the room, then recalculate everything that depends on it. Measure the space, decide which overall size (width, height or depth) you can't compromise on, and scale the parts connected to it. Redraw the plan with your numbers and make a fresh cut list before you buy any lumber.

Step by step

1. Measure the real space. Check width at the top, middle and bottom, since walls and floors are rarely square. Note baseboards, outlets, vents, door swings and sloped ceilings. Use the smallest measurement.
2. Set your target size. Subtract a small working gap for pieces that slide into an alcove. A snug fit is hard to install if the wall bows.
3. Find what controls what. On a bookcase, a wider case changes shelf lengths, top and back panel size, and possibly shelf thickness. Height usually changes only the sides and back. Write down each affected part.
4. Keep the joinery sizes. Change part lengths and widths, not the thickness of stock or the size of joints. Mortises, dadoes and screw spacing generally stay the same.
5. Check strength. Long shelves sag. As a rule of thumb, a wide span in thin solid wood or plywood may need a thicker board, a front edge strip or a center support. If the piece will carry heavy loads or is tall, think about stability and anchoring it to the wall.
6. Redraw and recut the list. Sketch it full size or on paper with every dimension. Then compare the new list against standard board widths. Nominal and actual sizes differ, so see Reading a Materials List.
7. Test before cutting good wood. Cut cardboard or scrap templates, or mock up the footprint with painter's tape on the floor.

Recommended for youWhy Woodworking Builds Fail: Common Causes and How Better Plans Prevent Them

Where this goes wrong

• Scaling only some parts, leaving a cut list that no longer adds up.
• Ignoring the thickness of plywood or boards when working out inside dimensions.
• Resizing a plan whose original numbers were already wrong. Free PDFs especially deserve a check; see are free plan PDFs accurate enough.

If you're modifying a lot, a plan pack with clear dimensions and diagrams makes the job easier. Before you choose one, confirm what's included, including any editable or customizable formats, on the official Teds Woodworking site, and read our review for how it compares. For structural or heavy-load pieces, ask an experienced woodworker; see when to get support.

Related

• How to Plan a Woodworking Project Before You Buy Lumber
• Rescuing a Build From a Bad or Incomplete Plan
• Finding Good Woodworking Plans

Keep reading

Rescuing a Build From a Bad or Incomplete Plan: Fixing Missing Dimensions and Wrong Cut ListsYou've bought or downloaded a plan, started cutting, and something doesn't add up. A dimension is m…Class, Local Woodworker or Professional Help: When to Get Support Instead of Relying on Plans AlonePlans are good at telling you what to cut and in what order. They are poor at watching you cut it.…How to Plan a Woodworking Project Before You Buy Lumber: From Idea to Cut ListMost expensive woodworking mistakes happen before the first cut. A plan that looked complete turns…