Trusty Calculator
Transparent calculators for practical decisions
What it does
Trusty Calculator is a free library of 433 calculators for construction, finance, math, education, business, health, and unit conversion. Each tool aims to show the formula, assumptions, units, worked examples, and primary sources behind the result. No account is required.
Use 451 fast, transparent calculators for construction, finance, math, education, business, science, health, food, time, and everyday decisions.
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Most retirement calculators either oversimplify things or ask you to link your accounts so they can make money off your data. I wanted something that actually helped me see if I was on track without handing over a bank login, so I built RetireNumber. It's a privacy-first retirement planner. You type in your own numbers. No account linking, no selling your data, no VC. Just me and a subscription. The engine does real math: Monte Carlo with 1,000 runs, historical backtesting to 1928 using Shiller's Yale data, tax-aware withdrawal strategies, and scenario comparison so you can try different…
Calculator Center24d ago · calculatorcenter.online · ▲229 free calculators that show their work — no black boxes
More life & fun this month
the category →- TL
Life & fun · 10d ago · louisabraham.github.io
Photosynthesis fires two of your iPhone
Life & fun · 28d ago · photosynthesis.camera
SoloUno▲310Take control of hair pulling, nail biting & skin picking
Life & fun · 28d ago · solouno.io
Scroll through all 43,252,003,274,489,856,000 reachable Rubik's Cube permutations.
Life & fun · 26d ago · everycube.alen.is
Hi HN, I built Eigendrum, a web tool that solves the 2D wave equation for arbitrary shapes so you can hear what they sound like as drums. How it works: * Solves -∇²u = λu using finite element analysis (Kφ = λMφ) on a triangle mesh. * Validated to <0.1% error against closed-form solutions for circles (Bessel zeros) and rectangles. * Sound model factors in strike location, Rayleigh damping, and mallet width. * Includes Kac drums I & II to demonstrate identical sound spectra from different geometries. * No frameworks, build steps, or dependencies. Repo and tests:…
Life & fun · 27d ago · baselashraf81.github.io
Launched alongside, August 2026
the whole month →- TL
Life & fun · 10d ago · louisabraham.github.io
- SA
Hello HN! I found that picking out plausible but diverse skin tones for my digital art and game development projects was kind of difficult, and I got curious about if there was a way to define a color space that made it easy. I've built a color picker and procedural generation algorithm based on the space as well as a bunch of other fun js features and demos throughout the page that use the equations. If you find it interesting, I have lots of explanations of how I built it and what properties the space has. The methodology might be a bit shaky, but hopefully the result is as helpful for…
Life & fun · Aug 2026 · toneyalexander.github.io
I trained a 125M-parameter transformer to autocomplete piano performances in real time (~108 notes/sec on an iPhone 15). The idea is basically GitHub Copilot or Tabnine, except instead of prompting it with code, you prompt it by playing a few notes on a MIDI piano. The model then continues what you played, entirely on-device. The app is free if anyone wants to try it. Happy to answer questions about the model, training, Core ML, or the many things that didn't work.
AI · 17d ago · simedw.com