Work it out.
Calculators
Colour mixing
Ratio arithmetic
Bleaching: powder and developer
Producentdata (Wella Blondor)
Developer: volume to percentage
Branchekonvention (1 vol ≈ 0,3 % H₂O₂)
Mix two developer strengths
Blandingsregning (vægtet gennemsnit)
Grey coverage: proportion of natural shade
Producentdata (Wella Koleston Perfect grå-guide)
Colour cost per treatment
Kalkulation (forholdsregning)
Treatment price incl. VAT
Kalkulation · Momsloven (25 %)
Contribution margin per treatment
Regnskabslære (kalkulation)
Capacity: customers per day
Costing
Chair hire: what is left over?
Kalkulation (branchepraksis: fast leje eller omsætningsandel)
The customer's value per year
Costing
Hair growth: time to desired length
Hårfysiologi (ca. 1 cm pr. måned)
Water consumption for hair washing
DANVA Vand i tal 2025 (variabel pris ca. 82 kr/m³)
Electricity consumption: hairdryers and heated tools
Fysik: kWh = W × timer / 1000
Barbicide: mix the disinfectant
Producentdata (Barbicide: 60 ml koncentrat pr. 950 ml koldt vand)
Shampoo: consumption and stock
Ratio arithmetic
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.