Today we are releasing the biggest content update since umrechner.online went live: 21 new calculators across three areas. The focus was not on quantity but on depth – every calculator works with the real formulas from standards, textbooks or professional practice, explains its calculation path and adds a professional interpretation of the result.
For the electrical trade: 6 professional calculators
Master electricians, journeymen and planners now get tools that are usually locked away in expensive trade software – from the disconnection condition per DIN VDE 0100-410 to current-carrying capacity per DIN VDE 0298-4 with installation method, temperature and grouping factors:
- Short-Circuit Current Calculator (Loop Impedance) – Calculate the prospective fault current Ik from the measured loop impedance Zs and verify the disconnection condition per IEC 60364-4-41 for MCBs and RCDs.
- Motor Calculator (Rated Current, Fusing, Supply Cable) – Calculate rated current, starting current, overload protection setting, back-up fuse and supply cable recommendation for three-phase and single-phase motors.
- EV Charger Calculator (Charging Time, Cable, Fusing) – Calculate EV charging time plus supply cable cross-section, fusing and RCD requirements for 3.7 to 22 kW wallbox installations.
- PV String Calculator (Inverter Sizing) – Size PV strings correctly: check open-circuit voltage at low temperature against inverter maximum DC voltage and the MPP window - with min/max module count.
- Lighting Calculator (Lumen, Lux, Number of Luminaires) – How many luminaires does the room need? Calculate luminous flux demand and number of fixtures using the utilisation factor method with EN 12464-1 target values.
- Cable Ampacity Calculator (with Grouping Factors) – Calculate permissible current-carrying capacity Iz per IEC 60364-5-52 methodology: installation methods A1-E, ambient temperature and grouping correction.
For high-purity gas and plant engineering: 7 specialist calculators
An area with hardly any usable tools online: calculators for everyone working with high-purity gases, vacuum and gas supply systems – featuring the Magnus formula, partial pressure blending, VDI/VDE 2173 and manufacturer conversion factors:
- Dew Point to ppm Calculator (Moisture in Gases) – Convert dew point to ppmv residual moisture and back - pressure-corrected using the Magnus formula, with mg/Nm³ and purity grade classification.
- Purge Time Calculator for Gas Lines – Calculate purge time and gas consumption for dilution purging of gas lines: t = V/Q × ln(C0/C) - for commissioning high-purity gas systems.
- Calibration Gas Blending Calculator (Partial Pressure) – Prepare gas mixtures by the partial pressure method: calculate fill pressures for component and balance gas from a target concentration in ppm or percent.
- Kv Value Calculator for Gases (Valve Sizing) – Calculate Kv and Cv values for gas flow per VDI/VDE 2173 - with automatic detection of subcritical vs. critical (choked) flow and 8 gases.
- Leak Rate Converter (Leak Testing) – Convert leak rates between mbar·l/s, Pa·m³/s, atm·cc/s, sccm and Torr·l/s - with helium-to-air equivalent and leak tightness classification.
- Cryogenic Liquid Calculator (LN₂, LO₂, LAr: Liquid ↔ Gas) – Convert cryogenic liquids: litres liquid, kilograms and normal cubic metres of gas for LN2, LO2, LAr, LHe and LH2 - with cylinder equivalent and holding time.
- MFC Gas Conversion Factor Calculator – Gas correction for thermal mass flow controllers: calculate real flow or required setpoint from the gas conversion factor (GCF) for 14 gases.
For everyday life: 8 new calculators
And since not every visitor runs a gas mixing plant, everyday tools got a major boost too – from the classics to hands-on trade helpers:
- BMI Calculator – Calculate your Body Mass Index with WHO classification, normal-weight range for your height and the corrected 'New BMI' (Oxford formula).
- Blood Alcohol Calculator – Calculate blood alcohol content using the Widmark formula: current BAC in per mille, time until sober and until below legal limits.
- Age Calculator (Age & Days) – Calculate your exact age in years, months and days – plus days lived, weeks, hours, weekday of birth and countdown to your next birthday.
- Working Days Calculator (Germany) – Calculate working days between two dates – with public holidays for each German federal state, weekends and optional vacation deduction.
- Shoe Size Converter – Convert shoe sizes between EU, US (men's/women's), UK, Japan/Mondopoint and foot length in cm – calculated via the foot length.
- Sleep Cycle Calculator – Calculate optimal bedtimes and wake-up times – based on 90-minute sleep cycles and your personal time to fall asleep.
- Roof Pitch Calculator – Convert roof pitch between degrees, percent and rise/run – including rafter length, pitch ratio and classification by roof type.
- Staircase Calculator – Calculate a staircase using the step formula: riser, tread, number of steps, run length and pitch angle – checked against DIN 18065 limits.
What comes next
All 21 calculators are free to use as of today – as always without registration and in all seven languages of the site. They are marked with a NEW badge on the homepage. Missing a calculator or spotted an error? Contact us via the contact form – the best new calculators grow out of real use cases.
