Work it out.
Calculators
Roof area, battens and tiles
Geometry · standard: Randers Tegl RT 823 (datasheet 2025)
Roof pitch: fall, percentage and ratio
Ratio arithmetic
Roofing felt: number of rolls with overlap and waste
Areal og forholdsregning
Roof outlets: number and drainage capacity
DS 432:2020
Tapered insulation: thicknesses and volume
Geometri — branchefald 1:40
Snow load on a flat roof
DS/EN 1991-1-3 + DK NA:2024
Wind zones on a flat roof: edges and corners
DS/EN 1991-1-4 (figur 7.6)
Ballast against wind uplift
Fysik (m = p/g) + branchekrav for ballasttage
Gas consumption: how long will the cylinder last?
Producentdata (Sievert) + propan 46,3 MJ/kg
Asphalt primer: litres and cans
Producentdata — tjek databladet
Runs and welded seams on the roof surface
Geometry
Slate: sprinkling the surface
Producentdata: typisk ca. 2 kg/m²
Dead load of the roof build-up
Producentdata — tjek databladet
Working hours and staffing
Ratio arithmetic
Material lift: pallets and weight on the crane
Forholdsregning + producentdata (rullevægt)
Edge profile — free bend profile in thin sheet
Exact flat pattern
Gutter — half-round, quarter-round and box
Exact flat pattern
Chimney flashing, 4-part
Exact flat pattern
Roof collar around a round pipe
Exact flat pattern
Vent cowl
Exact flat pattern
Valley and ridge
Exact flat pattern
Window sill — bottom flashing
Exact flat pattern
Rafter template
Exact flat pattern
Roof surface covering
Exact flat pattern
Tools that work in all subjects
Whatever your programme is called, these tools calculate the same — Pythagoras, area, percentages and units are not tied to one trade.
- 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.