Rupix Tools Blog

Guides worth the numbers

Deep dives on loan maths, taxes, passwords, tokens and image files — written around the free tools on this site. Nothing to install, nothing gets uploaded.

Security• 9 min read•

JWT tokens explained for developers

Anyone can decode a JWT — reading it proves nothing about trust. Learn the three-part structure, Base64URL quirks, registered claims and how to debug expiry timestamps correctly.

Read article
Home Loans• 9 min read•

How to calculate your home loan EMI correctly

EMI looks like one number, but banks build it from a formula you can verify in two minutes. Learn the reducing-balance method, the monthly-rate trap, and why early EMIs are mostly interest.

Read article
Security• 8 min read•

What makes a password strong (and what doesn't)

Length beats symbol soup. See why P@ssw0rd! fails, how entropy really works, what cracking wordlists already know about substitutions, and which habits genuinely protect accounts.

Read article
GST• 8 min read•

GST calculation mistakes small businesses make

Adding 18% and extracting 18% give different answers — and mixing them up misquotes every price you print. The GST calculation mistakes small Indian businesses make, with worked rupee examples.

Read article
Developer Tools• 7 min read•

The JSON mistakes that break APIs (and how to spot them fast)

Trailing commas, smart quotes and stringified numbers cause most JSON failures. Spot the eight mistakes that break parsers fast and fix them by line number instead of by feel.

Read article
Investing• 8 min read•

How much does a ₹5,000 monthly SIP really grow to?

A ₹5,000 monthly SIP grows to about ₹4.12 lakh in 5 years and roughly ₹25.23 lakh in 15 years at 12% — the plain-language maths behind compounding, inflation, step-up SIPs and costs.

Read article
Image Tools• 8 min read•

How to compress images without visibly losing quality

Shrink photos dramatically with no visible quality loss: pick the right format, hit the quality sweet spot, resize before compressing and keep everything on your own device.

Read article
Home Loans• 9 min read•

Prepay your home loan or invest the difference?

Prepaying a 9% home loan is a guaranteed, tax-free 9% return. Whether it beats investing depends on rates, taxes and temperament — a practical framework with rupee-level comparisons.

Read article
Security• 6 min read•

Checksums explained: verifying downloads with SHA-256

A checksum is a one-way fingerprint of your download. Learn how SHA-256 verification works, why MD5 and SHA-1 fell from grace, and how to compare hashes without uploading files.

Read article
GST• 7 min read•

GST-inclusive vs GST-exclusive: price without losing your margin

Promise a customer ₹999 inclusive of GST at 18%, and your net is ₹847.46 — not ₹819. Where inclusive vs exclusive pricing diverges, and the habits that stop the slow margin leak.

Read article
Exam Forms• 8 min read•

How to resize your photo and signature for online exam forms (UPSC, SSC, IBPS, NEET)

Exam portals reject photos over strict pixel sizes and KB ranges. Get UPSC, SSC, IBPS and NEET specs right the first time with a repeatable five-minute resizing workflow.

Read article