Work it out.
Calculators
Chimney draught (buoyancy)
EN 13384-1 · fysik
Clear area from pipe diameter
Geometri · Bygningsreglementet
Flue loss and efficiency (Siegert formula)
Siegert-formlen (industristandard i røggasanalysatorer)
Emissions corrected to reference oxygen
Forholdsregning · MST-emissionsgrænseværdier / Ecodesign-referenceilt
Chimney height above roof
Bygningsreglementet / brændeovnsbekendtgørelsen
Sweeping fee — price per chimney
KL og Skorstensfejerlaugets vejledende takster 2026 (lovpligtig skorstensfejning)
CO concentration and alarm time
DS/EN 50291 (CO-alarmstandarden)
CO2 emissions from heating oil and natural gas
Energistyrelsens brændværdier og emissionsfaktorer
Firewood consumption — stacked cubic metres for heating demand
Energiindhold i brænde (brancheoplysning)
Is the firewood legal to burn?
Brændeovnsbekendtgørelsen (BEK nr. 199 af 2022)
Profitability — payback period for energy optimisation
Forholdsregning · økonomi
Capacity — sweeps per working day
Ratio arithmetic
Heat loss through a building element
Fysik · transmissionstab (Q = U·A·ΔT)
Ohm's law and electrical power
Ohms lov / grundlæggende elteknik
Square-to-round transition
Approximate 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
Pipe-to-square transition
Approximate 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.