Calculators built around real household decisions
HomDera calculators are intended for practical decisions before renovation work or an equipment purchase, not simply for displaying formulas. You enter information that can be measured or found in product specifications: room length and width, wall height, door and window areas, appliance power, battery capacity, number of paint coats or an allowance for cutting and waste.
The result should be treated as a working estimate rather than a final specification. It provides both a figure and the reasoning behind it: why the number of packs may be higher than the measured area suggests, why paint coverage changes with the surface and number of coats, why a battery cannot normally deliver all of its rated capacity, and why electrical planning must consider circuit breakers, cable capacity, safety margins and installation conditions as well as total wattage.
- for floors — room area, cutting allowance, flooring or tile quantity, and the number of packs required;
- for walls — paint, wallpaper, tiles, door and window openings, coats of paint and wallpaper rolls;
- for electrical planning — combined appliance power, current, household load and an initial safety allowance;
- for batteries — expected runtime, required capacity, inverter losses and backup power for a boiler, heating system or essential home devices.
Avoid estimating room dimensions by eye when you can measure them properly. A difference of only a few centimetres along one wall may seem unimportant, but across an entire room it can be enough to change the amount of paint, wallpaper, tile or flooring you need.
Choosing the right calculation for your project
| Your project | What to calculate | What to consider |
|---|---|---|
| Installing a new floor | Flooring, tiles, room area, waste allowance and packs | Product dimensions, cuts, laying direction and spare material |
| Painting or finishing walls | Paint, wallpaper, tiles and wall area excluding doors and windows | Number of coats, pattern matching, uneven surfaces and openings |
| Reviewing electrical demand | Appliance wattage, estimated current and total household load | Starting currents, duty cycles, circuit limits and an appropriate safety margin |
| Preparing for power outages | Battery runtime, battery capacity, UPS sizing and boiler or heating backup | Inverter efficiency, depth of discharge, battery condition and actual connected load |
