Work it out.
Calculators tailored to the carpentry trade: measure the material consumption, divide the run into centre-to-centre spacing, find the rafter length, set out the staircase and work out the concrete. Enter your own values — the result updates live.
Step V — Directory
The guided workflow: answer house dimensions and chosen roofing material and get the complete roof specification brought together in one flow.
Step A — Measurement & material consumption
Start here: convert area into a number of boards/sheets and linear metres — with your own waste allowance.
Step B — Spacing & centre distance
Count rafters, battens and posts correctly over a span based on the centre spacing (cc).
Step C — Roof & rafters
Find the rafter length and roof pitch of a symmetrical gable roof using Pythagoras.
Step D — Stairs
Set the riser, going, and number of steps according to Blondel's stride formula.
Step E — Concrete & foundation
Calculate the concrete volume for a rectangular pour, so the concrete can be ordered in one go.
Step F — Building physics & material
Wood moisture and shrinkage, U-value against BR18, and how much cross-section burns away — the trade's physics check.
Shrinkage & moisture movement
Dimensional change with changing wood moisture
U-value — timber-frame wall/roof/floor
Heat loss through a flat construction
BR18 climate requirement — LCA against the limit value
Climate impact per m² per year compared with § 298
Fire charring & residual cross-section
How much wood burns away over time
Vapour barrier Sd-value
Diffusion resistance for a layered vapor barrier
Step G — Plot & siting
The house, carport or shed on the plot: distance and height to the boundary under the building right.
Tools that work in all subjects
Maths and templates that work in every trade — and at school. Every tool shows the formula and the working with your own numbers.
- Pythagorasa² + b² = c²Find the missing side, set out a right angle, check whether a room is square, and find the space diagonal.
- Area and perimeterm²Rectangle, triangle, trapezium, circle and composite shapes — area and perimeter.
- Volume and surface aream³ · lBox, cylinder, cone, sphere, pyramid, prism, pipe and frustum — also in litres.
- Percent%Percentage of, how many per cent, percentage change, discount and VAT.
- Scale and ratios1 : 50From drawing to reality, area and volume to scale, the rule of three and dividing in a ratio.
- Unit convertermm ↔ mFrom mm to km, Pa to bar and kB to GB — with the unit staircase.
- Time calculations and the clockt : minTime between two clock times, add time, and 1.75 h = 1 h 45 min for the timesheet.
- Slope and fall% · ° · 1:xFall from level to level, in per cent, per mille, degrees and mm per metre — and the height difference.
- Material consumption including wastem² + %Boards, paint, battens at c/c spacing and packs — for a composite surface or a whole room, with waste.