Tools
- How I calculate age accurately for forms and records
Age sounds simple, but exact age depends on the date you measure against. The Age Calculator tool handles the repetitive part so I can focus on checking whether the result makes sense.
- How I calculate discounts before buying
Discounts are easier to compare when I calculate the final price instead of only reading the percentage. The Discount Calculator tool handles the repetitive part so I can focus on checking whether the result makes sense.
- How I calculate interest without hiding the assumptions
Interest calculations depend heavily on method: flat, effective, annuity, compound, tiered, or after-tax. I use Interest Calculator for the quick version of this task, then I review the output before relying on it.
- How I calculate loan payments before borrowing
A loan calculator helps me see the monthly payment, total interest, and how extra payments change the schedule. I use Loan Calculator for the quick version of this task, then I review the output before relying on it.
- How I calculate percentages without doing mental math
Percentages are simple until the question changes: percentage of, percentage increase, percentage decrease, and reverse percentage are different tasks. The Percentage Calculator tool handles the repetitive part so I can …
- How I check a file hash before trusting a download
When I download an installer, ISO image, backup, or release archive, I sometimes see a checksum published next to it: SHA256: 4a1f... That checksum is there so I can check whether my downloaded file is exactly the same …
- How I check a JWT when an API login looks broken
A JWT is one of those strings that looks scary the first time you see it. It often appears in a login response, browser storage, or an API request header:
- How I check a PDF digital signature without confusing it with a drawn signature
A PDF digital signature is cryptographic metadata. It is not the same thing as an image of a handwritten signature placed on a page. The PDF Signature Checker tool gives me a safe place to test the idea before I put it …
- How I check an IBAN before using bank details
An IBAN check can validate structure and check digits, but it does not prove the account belongs to the intended person. The IBAN Validator tool helps me inspect the input and output without writing a one-off script …
- How I check an IP address without overtrusting geolocation
An IP lookup can show useful network context, but it does not prove a person’s exact physical location. The IP & Geolocation Lookup tool helps me inspect the input and output without writing a one-off script …