How do I use the computers?

The use is very simple:

1. Select a computer: Search the desired computer via search or categories
2. Enter values: Fill out the input fields (all with placeholders and help texts)
3. Calculate click: Click on the orange "Calculate" button
4. Result reading: The result will be displayed immediately, including formula and explanation

Tip: Only the relevant fields are automatically displayed for computers with drop-down selection (e.g. "Calculate Areas"). With "circle" you only see the radius, with "rectang" only length and width.

Why are some input fields excavated or disappear?

This is an intelligent function! Many computers support various types of calculation. For example, Volume calculator Select "Kugel" will automatically display only the relevant fields (Radius). Fields for rectangle (length, width) are hidden.

So we avoid confusion and you always only see what you really need.

What do the help texts mean under the input fields?

The help texts (in beige boxes with info icon) explain what is to be entered in the respective field. They often also give example values or hints:

• "Typically: 0.8-1.5 seconds" in the brake travel computer
• "Average Germany 2025: approx. 0.30 €/kWh" in the electricity cost calculator
• "Let GENAU empty a field - this is calculated" at the Pythagoras calculator

Can I change the units?

The easy conversion (e.g. length calculator, weight calculator) you can choose from many units and convert them as desired.

The scientific computers (e.g. Pythagoras, volume) the units are fixed, since the formulae are specific. The most common units (cm, kg, m/s) are preselected.

What does "formula" mean in the results?

We show the formula used for each scientific computer so that you can understand how the result was calculated. For example:

• Pythagoras: c = √(a2 + b2)
• Volume ball: V = 4/3 × r3
• Force: F = m × a

You will also learn the mathematical and physical basics.

Are the calculations correct?

Yes! All calculations are based on scientifically recognized formulas and methods:

• Physics calculator: Official SI units and physical laws
• Mathe-Rechner: Mathematically exact formulas
• Financial account: Current tax rates and social charges 2025 (Germany)
• Craftsmen: Standard industry standards and empirical values

Important: Some computers (e.g. gross net, cooking times) use simplified calculations or averages. For legally binding information please consult a person skilled in the art (tax consultant, Statiker, etc.).

Why does my gross net result deviate from my payroll?

Our gross net calculator uses one simplified but realistic Calculation based on the current tax rates 2025. Deviations may arise from:

• Amounts (e.g. advertising costs)
• Special arrangements for your health insurance
• Capital benefits (VWL)
• Occupational pension provision
• Short-time work or special payments

For an exact calculation, contact your employer or tax advisor.

How current are your data?

We regularly update our computers:

• Rates: Stand 2025 (fund 12.096 €, social contributions 2025)
• Physical constants: Most recent SI definitions (g = 9.81 m/s2, π = 3.14159...)
• Currency exchange rates: Sample courses (static) – future live courses planned
• Materials: Standard density according to DIN/ISO

Can I rely on the results?

Our computers are ideal for:

• planning and oversight calculations
• ‡ homework and learning
• everyday questions (sprit costs, electricity costs, etc.)
• └ Projects (Heimwerken, Cooking, etc.)

But: For legally binding, safety-relevant or professional calculations (statistical, electrical installation, tax return), please consult a specialist.

How do I find the right computer?

We offer three options:

1. Search function: Simply enter a keyword at the top right (header), e.g. "percent", "Brutto", "Pythagoras". The live search immediately shows matching computers.
2. Categories: Click on Categories and select the area (e.g. "Financial & Taxes" or "Physics & Science").
3. Home: On Home you will find the "Family used computers" – these are the most popular tools.

What is the difference between "Calculator" and "Converter"?

We distinguish two types:

• Converter (converter): Simple unit conversion without formula. Example: "100 meters in kilometers" → only factor 0.001
• Calculator: Calculation with real formulas. Example: "volume of a sphere with radius 5 cm" → V = 4/3 × π × r3

Most of our modules are Calculator, as these provide more added value.

Is there a mobile app?

Currently not, but our website is fully mobile-optimized. It works on all devices (smartphone, tablet, PC) perfectly in the browser. Just save a bookmark on your home screen.

Are my inputs stored?

No. We do not store personal data or your input values. Only anonymous usage statistics (e.g. "Rechner X has been used 100 times") are collected to identify the most popular computers.

Your calculations remain private and local in your browser.

Which browser do I need?

Our website works with all modern browsers:

• Chrome / Edge (version 90+)
• ʿ Firefox (version 88+)
• ‡ Safari (version 14+)
• Opera

JavaScript must be enabled as our computers are interactive.

Why does an error message appear?

Common causes:

• "Please enter a value": You left a mandatory field empty
• "Invalid value": You entered text where a number is expected
• "Time must be greater than 0": Logical error (e.g. division by zero)

Check your inputs and pay attention to the placeholders (e.g. "e.g. 5"). For technical problems, reload the page (F5).

Can I print or store the results?

You can easily print the page with the results (Strg+P/Cmd+P) or take a screenshot. An export function (PDF, CSV) is planned for the future.

Gross net calculator: Can I also calculate net to gross?

Yes! Our gross net gross calculator works in both directions:

• Gross → Net: You know your gross salary and want to know what remains
• Net → Gross: You have a desired net content (e.g. € 2,500) and want to know what gross is required for this

Simply select the desired direction in the first drop-down field.

Pythagoras-Rechner: How do I give up the missing page?

Just leave exactly one field blank (or 0). The computer automatically detects which page is missing and calculates:

• a=3, b=4, c=leer → calculated c (hypotenuse)
• a=leer, b=4, c=5 → calculated a (cathete)
• a=3, b=leer, c=5 → calculated b (cathete)

Volume calculator: Which forms are supported?

Currently 6 geometric shapes:

• Ball: V = 4/3 × r3
• Cylinders: V = π × r2 × h
• Cubes: V = a3
• Quader: V = l × b × t
• Pyramid: V = 1/3 × G × h (quadratic base area)
• Cones: V = 1/3 × r2 × h

Further forms (cylinder segment, prism, etc.) can be added upon request.

Sprit calculator: How do I know my consumption?

You can find your average consumption:

• In On-board computer your car (often as "Ø l/100km")
• In Vehicle licence (combined consumption)
• Calculate yourself: full tank → km drive → refuel → fried liter / driven km × 100

Kitchen dimensions: How much is a "cup" exactly?

We use the American Standard:

• 1 cup (coup): 240 ml
• 1 tablespoon (EL): 15 ml
• 1 teaspoon (TL): 5 ml

Note: That's the VOLUMEN. A cup of flour weighs differently than a cup of sugar! For exact weights please use a kitchen scale.

Are you offering an API?

Currently we have Internal API for our website. One public API for developers is in planning (version 5.0, probably Q2 2025).

The API will provide access to ALL computers, with automatic integration of new computers. Sign up for our newsletter to be informed.

Will the API be paid?

Yeah, but with one generous free rate:

• Free: 100 requests/day (free)
• Basic: 10,000 requests/month (~10 €/month)
• Pro: 100,000 requests/month (~50 €/month)
• Enterprise: Unlimited

Follow details at Launch. See also: API documentation (in preparation).

Can I connect the computers to my website?

Currently not directly. With the coming API you will be able to integrate all computers into your own applications (by REST-API). A Embed widget (iFrame) is also planned for the future.

What data do you collect?

We collect Minimum data:

• Anonymous usage statistics: Which computer was used as often (without personal data)
• Server logs: IP address, browser, access time (standard, 7 days storage)

We collect NO:

• ❌ input values (your calculations remain private)
• ❌ Personal data (no registration required)
• ❌ Tracking via third-party providers (no Google Analytics, no Facebook Pixel)

Details: Privacy Policy

Are cookies used?

We use only technically necessary cookies:

• Session cookie (for admin login)

No tracking cookies, no advertising cookies, no third party cookies.

Is the connection safe?

Yeah. Our website uses HTTPS encryption for all connections. In addition, we use modern security heads (X frame options, CSP, etc.).

Does the page work on the smartphone?

Yeah, perfect! Our website is fully responsive and optimized for mobile devices. All computers work on:

• 📱 Smartphones (iOS, Android)
• 📱 Tablets (iPad, Android tablets)
• 💻 Desktop (Windows, Mac, Linux)

Can I add the page to the homescreen as an app?

Yes! Here we go:

• iPhone/iPad: Safari → Share button → "Zum Home screen"
• Android: Chrome → Menu (3 Points) → "Add to Start Screen"

Then you have quick app-like access to all computers.

How can I count faster?

Tips:

• Use the Tab button to change between fields (faster than mouse)
• Press Enter to calculate (instead of clicking on button)
• Sit Bookmark for often used computers
• Use the Search function in the header (click more quickly than by categories)

Can I suggest improvements?

Absolutely! We are looking forward to:

• Proposals for new computers
• Error messages
• Improving ideas
• Feature-Wunsche

Contact us about the Contact form or by email.

Why is there no computer for [XYZ]?

We continuously expand our offer! At the moment we have most requested calculations focused (finance, mathematics, physics, everyday life).

If you miss a specific computer, write us – if the demand is large enough, we will build it!

Can I use the computers for homework?

Yes! Our computers are ideal for:

• Check homework (mathematics, physics)
• Learning formulas (we show the formula for each result)
• Understanding step-by-step explanations

Tip: Try to count yourself, then check with our computer. How to learn best!

Are the computers suitable for study?

Yes, for basics and surpluses. Our physics and mathematics calculators use the standard formulas that are also taught in the university.

For complex scientific calculations or tests, however, you should use specialized software (MATLAB, Wolfram Alpha, etc.).

I have a question that is not answered here.

No problem! Contact us:

• Contact form: Contact
• E-mail: support@umcomputer.online

We usually respond within 24-48 hours.