Interior Design by the Numbers: Space Planning, Clearances, Rugs, Curtains, Wallpaper & Budgets

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Calculate the area of five rooms, the share of each floor left free after the furniture goes in, the total floor area of the flat and how many rooms fall below the studio's free-floor guideline.
• Look up the minimum for six measured gaps, flag each one as Tight, OK or Generous with IFS, calculate a viewing distance from the screen size and test whether the sofa sits close enough to it.
• Work out the longest rug that leaves an even floor border, pick the largest standard size that fits with an approximate XLOOKUP, check that the front legs of the seating stand on it and calculate how much of the floor it covers.
• Turn track widths into the number of fabric widths with a fullness ratio, round each cut length up to the pattern repeat, calculate the metres of fabric per window and price the whole order.
• Count the strips for four walls, round each cut length to the pattern repeat, find how many whole strips one roll gives and order the right number of rolls – and see why the area method falls short.
• Measure the three legs of the work triangle between sink, hob and fridge from plan coordinates with SQRT, flag a leg outside the guideline, add up the triangle and test it against a minimum and maximum with IFS.
• Find the nail height for three prints from a centre height and the wire drop, measure the width of the group above the sofa and its share of the sofa width, and space four frames evenly along the hall wall.
• Total the shopping list by room with SUMIFS, find the share of the budget that the must-have items take, turn lead times in working days into delivery dates with WORKDAY and chart the spend per room.