Calculators that end in a drawing.
Small, fast, honest about their assumptions, and metric throughout. Each one solves the arithmetic of one job — and each answer is a step from a measured floor plan, because a quantity you computed from a guessed room size is still a guess.
No account, no modal in your way, and a result you can share by copying the URL — the numbers you type travel with the link.
The U-value calculator also reads from GridSnap Materials — named insulation products with the conductivity their manufacturer declares, and the document that declares it.
Room area to packs and cost — waste allowance by laying pattern, pack coverage, price per pack; handles L-shaped and combined-rectangle rooms with a live shape preview.
Wall area to litres — doors and windows subtracted at standard sizes, coats and spreading rate adjustable.
Floor-to-floor height to riser count, riser height, going, pitch and total run — checked against the 2R+G comfort rule.
Convert between paper millimetres and real metres at 1:20–1:500, or find the scale of a drawing from one known dimension.
Stack real construction layers — or your own materials — into a hatched section drawing, get the U-value (EN ISO 6946 form), and the insulation thickness needed to reach a target.
The calculator is the easy half
Every one of these formulas takes a room size as input — and the room size is where quantity estimates actually go wrong. A tape measure across a cluttered room, a guessed wall height, an L-shape "roughly" split into rectangles: the formula then faithfully multiplies the error.
That is why each calculator hands off to the Gridsnap editor: draw the room once in exact millimetres — or trace the plan you already have — and areas, perimeters, wall lengths and opening sizes stop being estimates. The numbers these pages approximate with standard sizes, a drawn plan simply knows.
Draw the room the numbers came from
Free browser CAD in millimetres: plans, elevations, 3D, vector PDF and DXF export. No account needed to start.