Big financial decisions are hard because everything interacts: mortgages, debts, investments, retirement contributions, and more. It's hard to see how a decision like buying a house, upgrading your car, or retiring early plays out when all of those factors move together at once.
I found that the solutions that existed didn't really help me answer my financial questions. Spreadsheets were too brittle and error-prone, and they're a pain to use. One-off calculators were too narrow and didn't take the whole financial picture into consideration. Other financial planning software ends up being expensive, bloated, and they don't clearly give you an answer.
ifso is a financial simulator I've spent hundreds of hours building and personally use. It's for DIY planners, such as people who want to see how major decisions play out before committing, the FIRE crowd checking whether they can actually retire early, etc. The goal was to give a simple interface that handles all of the complexity for you and gives you a clear answer on how your financial plan works out.
Your numbers are entered via manual input, so no bank or account linking to ensure your privacy. A guided setup takes your age, income, and accounts across eight asset types, from brokerage, 401(k), and Roth to homes, cars, and loans. From there, you add life events pinned to ages: buy or sell a home or car, retire, claim Social Security, take a raise or pay cut, make a one-time purchase, and many more.
It's all one connected model, so a raise, a mortgage, and a retirement date move together. The engine projects year by year with real tax math (federal brackets, FICA, capital gains, and more) and handles retirement drawdown properly: withdrawal ordering across account types, a pre-59.5 bridge, Social Security timing.
Instead of just a chart you have to interpret, you get a plain-English verdict that tells you if your money lasts, what breaks, and when. You can also create multiple scenarios, where you duplicate an existing plan, tweak a few things, and compare them side by side to see exactly what impact a decision would have. Monte Carlo runs your plan through 1,000 simulated market histories for a probability of success, since markets don't have a static rate of return.
ifso is live at https://ifso.io. The free tier includes the entire simulation engine. Pro adds additional scenarios for side-by-side comparison and Monte Carlo.
If you give it a shot, I'd love to know what you think! I'm constantly working on improving the product and adding more features. Ultimately I want this to be a genuinely helpful tool for anyone planning their financial future.
I'm also happy to answer any questions here! For additional context, ifso is privacy focused, so your data is never shared or sold, and you're always able to download or delete your data. One requested feature was being able to convert properties into rental properties, which I thought was a really neat thing to simulate. I'm actively working on building this out now, and I hope to continue letting users build the scenarios they want to see and plan because the product is ultimately for you all!