Tools
Small, single-purpose web tools by Rahim Nathwani. Everything runs in your browser.
Documents & images
PDF Diff
Show differences between two PDF files visually.
Report Card Highlighter
Upload a PDF report card and highlight rows by E, R, or P rating — processed entirely in your browser.
Markdown Cleaner
Clean AI-generated markdown for Google Docs compatibility.
Markdown → EPUB
Convert Markdown to a valid EPUB 3 file in your browser.
JPEG Compressor
Compress images with adjustable quality and compare file sizes.
Passport Photo Montage
Make a 3×2 montage from one photo. Print at 4×6 for six 2-inch passport photos.
DTF Halftone Knockout
Knock out the shirt color as halftone dots for breathable Direct to Film transfers.
Snellen Eye Chart
Printable eye chart PDF sized exactly for your test distance and paper.
Work
Meeting Scheduler
Propose meeting slots and copy a message with one-click Outlook/Google calendar invite links.
Org Chart Builder
Upload an Excel file of employees and generate an org chart with SVG, PNG, and Mermaid exports.
Payment Plan Calculator
Generate NPV-based payment schedules for property purchases.
Excel Skills Survey
Self-assess your Excel skills and download a PDF report to share with your manager.
Maps & places
Zip Code Mapper
Draw polygons on a map to analyze which USA zip codes are enclosed.
SF POPOS Finder
Find San Francisco's privately owned public open spaces, sorted nearest first.
Lyft Bike Finder
Find nearby Lyft bike stations with real-time availability.
Museum Finder
Find museums by distance, type, and reciprocal network membership.
El Gouna Restaurant Finder
Find El Gouna restaurants by distance, cuisine, and dining type.
El Gouna Nearby Units
Find the 5 nearest El Gouna units and buildings to your location.
California schools
School Finder
Find Bay Area private schools by grade, tuition, and location.
SAT Explorer
Compare California high-school SAT scores 2017–2020: trends over time, subscores, and participation.
CAASPP Explorer
Explore California standardized test scores by school, district, and demographic group.
UC vs SBAC
Compare UC freshman admissions with grade-11 SBAC math performance across California public high schools.
Probability & statistics
Distributions & Percentiles
Learn how to calculate percentiles and visualize data distributions.
Galton Board
Visualize publication bias: drop balls through a peg board and see how selecting only significant results distorts the distribution.
Berkson's Paradox
See how selection bias creates spurious correlations between independent variables.
Monty Hall Simulator
Play the three-door game and watch how often you win track how often you switch — converging on the 1/3 vs 2/3 result.
Investment Challenge
Read each deal's odds, decide whether to bet and how much, and learn position sizing and the Kelly Criterion.
Simulations & explainers
Flock
Experiment with a mathematical model of birds in flight: three simple rules with no leader produce a starling murmuration.
Oscylinderscope
Pluck strings against a spinning striped drum and watch their sound waves freeze or drift via persistence of vision.
Jevons Paradox Simulator
Simulate how efficiency gains can paradoxically increase total resource consumption via the rebound effect.
Modeling Mixture Problems
Learn to solve mixture problems with an interactive tutorial.
The Invention Dig
Scroll down through 3.3 million years of strata to see when everything was invented — and which came first.
Word Jumbler
Scramble words while keeping first and last letters intact.
