Contact

How to reach us

The only contact channel for this site is GitHub Issues. Email and phone enquiries are not accepted. Opening an issue requires signing in to a GitHub account. The site is run by one person, so response times cannot be promised, but issues are read and answered with a note on whether a fix was made.

GitHub Issues is a public board that anyone can read. Do not post personal information such as your name, email address, phone number, employer or address, internal company material, or design values that must stay confidential. If you posted something by mistake, you can edit or delete it yourself, or ask the operator to hide or delete it.

What you can raise

• A result that disagrees with the formula or a textbook value
• Errors in a guide’s explanation, units or sources
• Broken links, layout problems or buttons that do not work
• Awkward or inconsistent Korean and English text
• Suggestions for new dimensionless numbers or examples
• Questions or requests about the privacy policy

Reviews of specific designs and guarantees of results are not offered. See the terms of use for how results may be used.

What to include in an error report

The following details let the operator reproduce the problem and find its cause quickly.

1. The page address and calculator (for example /en/calculators/reynolds, Reynolds number)
2. The values you entered and the unit of each, exactly as typed
3. The result shown on screen
4. The value you expected and where it comes from (textbook and page, paper, or your own working)
5. For display problems, your browser and device

Title: [Reynolds number] Result differs from textbook example
Page: /en/calculators/reynolds
Inputs: ρ = 998 kg/m³, v = 1.5 m/s, L = 0.05 m, μ = 0.001 Pa·s
Result shown: (value on screen)
Expected value and source: (textbook and page, or working)

The numbers above only illustrate the format. If you cannot cite a source for the expected value, include your working and it can be checked together.

Reports that are easy to reproduce, and reports that are not

The same problem can take very different amounts of time to check depending on what the report says. The two reports below are hypothetical examples describing the same situation.

• Hard to check: “The Reynolds calculator seems wrong.” There is no way to know what was entered or what it was compared with, so the operator cannot reproduce the result.
• Easy to check: “On /en/calculators/reynolds I entered ρ = 998.2, v = 1.2, L = 25, μ = 0.001 and got about 2.99 × 10⁷. The textbook example gives about 30,000.” This shows immediately that the 25 mm diameter was entered without converting to metres. 25 mm is 0.025 m, which gives Re ≈ 29,946 and agrees with the textbook.

For layout problems or buttons that do not respond, these details help: browser name and version, device type and screen width (for example, a phone in portrait), whether the dark theme or Korean interface was on, whether the problem always or only sometimes happens, and if possible any error message from the browser’s developer console. If you attach a screenshot, check that the address bar or other tabs do not show personal information.

What happens after you report

1. The operator reads the issue and recalculates with the same inputs.
2. If information needed to reproduce the problem is missing, the operator asks in an issue comment.
3. If it is an error, the page is fixed; for a numerical error the corrected value is also added to the test script (tests/check_calculations.cjs). The fixing commit is linked from the issue and the issue is closed.
4. If it turns out not to be an error (for example, the textbook used a different characteristic length), the reason is explained in a comment.

The site is run by one person in spare time, so there is no fixed turnaround. Fixes appear on the site after deployment, and the change history before and after deployment is visible in the repository’s commit history.

Before you report

Units are the most common reason a result looks wrong. Check that lengths were not entered in mm, viscosity in cP or specific heat in kJ. Swapping dynamic viscosity μ with kinematic viscosity ν, or using a different characteristic length from your textbook, also changes the value. Each calculator page lists the usual conversions in its variables table and unit notes. If a difference remains after that, please report it.

Privacy requests

Requests to access, correct, delete or stop processing personal information are also handled through GitHub Issues. Even if the request involves personal information, write only the type of request in the issue; the operator will reply in the issue with the next steps. Data used for statistics and advertising is processed directly by Google and Microsoft, so you can adjust it immediately through their settings pages. Details are in the privacy policy.