Alternatives
Products that do what 401K-O does
The 401k maxing calculator that should have already existed.
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- 2IQ
Quick background: I used to code. Studied it in school, wrote some projects, but eventually convinced myself I wasn't cut out for it. Too slow, too many bugs, imposter syndrome — the usual story. So I pivoted, ended up as an investment associate at an early-stage angel fund, and haven't written real code in years. Fast forward to now. I'm a Buffett nerd — big believer in compound interest as a mental model for life. I run compound interest calculations constantly. Not because I need to, but because watching numbers grow over 30-40 years keeps me patient when markets get wild. It's basically…
Jan 2026 · calquio.com
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- 4IC
2018 · investmentcalculator.io
- 5AF
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…
Feb 2026 · retirenumber.com
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2013 · kivalia.com
- 7IG
I’ve always found that online calculators tend to have bad UIs, especially on mobile. Most of the calculator websites I’ve come across use outdated and inconvenient ways of inputting data, or they format the results in confusing ways. I’ve noticed that fraction calculators (especially mixed fractions) are terrible to use, even on desktop. I haven’t built one of those yet, but it’s something I’m planning to tackle soon. This is a project I’ve always wanted to work on, but I’m relatively new to this space. So far, I’ve created a collection of simple calculators focused on math and finance. I’d…
2025
- 8TF
After having been a regular employee for years, I worked as a freelancer for a while. Going into my freelancing life I had no real mental model for how much of the money I earned was truly mine to spend, and how much of it I needed to set aside for taxes, vacations, retirement, and in case I got sick. I modelled this in Excel as best I could and was quite surprised both by how complicated it was to get right, and how much money I actually needed to set aside! As my girlfriend also started freelancing last year, I decided to turn my Excel sheet into a little program she could use too, and in…
2022
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Free hourly to salary & take-home tax calculator
Jul 2026 · globaltoolsbox.online
- 11IM
Hi HN, I am a solopreneur in the evenings and a software engineer during the day. In the past, I have created lots of calculators for my web projects and freelancing friends. These were pretty basic, but users always welcomed them. I also used currently available builders, but the problem was that they were either slow, broke on mobile devices, had nonsense page view limits, or were expensive. Some even ticked all those boxes. So I have decided to create my own, with a simple interface, and called it Creative Widgets (if it ever takes off, I plan to add more exciting stuff like charts, etc,…
2024 · creativewidgets.io
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- 14IB
A few years ago, I started managing my finances using Google Sheets. It worked fine for a while, but then I hit some limitations. As my financial planning needs grew more complex, I found myself struggling with tracking assets and forecasting future financial scenarios. Thus, I started to work in my spare time on building FinancialAha: https://www.financialaha.com - a financial planning app designed to do everything my spreadsheets couldn’t. It is completely free and I intend to add some paid features later on as listed on the pricing page, but I want to keep it free for people…
2024
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Free financial calculators — no sign-up needed
Jun 2026 · tools.moneydecoded.net
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Advanced compound interest calculator with 60+ currencies
Jul 2026 · globaltoolsbox.online
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25 free calculators - your numbers never leave your browser
Jul 2026 · moneycrunchlab.com
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- 23IB
2019 · getretire.com
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