Hi Product Hunt! I’ve been building software for more than 20 years, and somewhere along the way, I got really interested in investing. I learned investing the hard way by putting real money into the market and quickly discovering how much I didn’t know. A few painful lessons later, I became far more interested in understanding how long-term investing actually works and how small decisions compound over time. As I started digging into the numbers, I found myself constantly running different scenarios. What if I invested a little more each month? What if the return was lower? How much difference would another five years make? What would it actually take to reach my goal? Being a software developer, I started building something. That something became CompoundFX. Most compound interest calculators could tell me what I’d have after I plugged in all the numbers. What they couldn’t tell me was what it would take to get there. That idea became Goal Mode. Set a target like $1M by 60, and CompoundFX works backward to figure out the missing piece. That might be the return you need, how long it will take, what you need to start with, or how much you need to contribute. I also cared a lot about privacy. These financial scenarios are personal, and I don’t think you should have to give up your data just to run some numbers. CompoundFX runs fully offline with no accounts, analytics, or data collection. Your numbers never leave your device. The iOS app is free to download and includes the full calculation engine, live growth charts with milestones, year-by-year breakdowns, and inflation, tax, and fee adjustments. A one-time $4.99 purchase unlocks Goal Mode, unlimited saved scenarios, side-by-side comparisons, and PDF reports. It's not a subscription! There’s also a free web calculator at compound-interest-calculator.app if you just want to run some numbers without downloading anything. I’d love your feedback!

CompoundFX: Compound Interest Calculator

Know what you’ll have and what it takes to get there.

Know what you’ll have and what it takes to get there.