SAVEcompound
Savings Goal Calculator — 3-Unknown Solver
The Savings Goal Calculator solves backwards for any one of three unknowns: given a target (e.g. $100,000), specify any two of {starting amount, monthly contribution, time} and we'll solve the third exactly. Use it for down payments, emergency funds, college savings, or any long-term goal.
Updated: ·See data sources
§ 01
How to use
- Pick the unknown. Monthly contribution, time, or starting amount.
- Enter the other two. Plus the target and assumed annual rate.
- Read the result. We show the value you need to reach the goal.
§ 02
Key features
Solve for contribution
Have target + start + time → required monthly?
Solve for time
Have target + start + monthly → how long?
Solve for start
Have target + monthly + time → starting amount needed?
Monthly compounding
Standard FV formula — not an approximation.
Contributed vs interest
Shown separately to clarify growth composition.
8 currencies
USD, EUR, GBP, SGD, INR, AUD, CAD, VND.
§ 03
Why Treasury.to?
- 3 different solver modes
- Closed-form + bisection
- Multi-currency
- Instant
- Free
- Mobile-first
§ 04
Frequently asked questions
01Is the solver penny-accurate?
Yes — contribution and start modes use the closed-form FV annuity formula. The time solver uses 200-iteration bisection accurate to under 0.05 months.
02What compounding does it use?
Monthly by default, matching savings accounts and ETF DCA. For other frequencies, use the Compound Interest Calculator.
03Can I model irregular contributions?
Not here — this tool assumes a constant monthly amount. Use the Compound Interest Calculator with 'both deposits & withdrawals' for irregular flows.
04What rate should I assume?
US high-yield savings: 4–5%/year. Total-market index funds long-term: 7–10% pre-tax. Pick a rate you trust yourself to stick with for the full horizon.
05Do I need to account for inflation?
Yes — use a real (after-inflation, ~3% subtracted) rate so your goal stays in today's purchasing power and doesn't need a later adjustment.
06What's a typical savings goal size?
Emergency fund: 3–6 months of expenses. House down payment: 20% of price. 4-year US college fund: ~$120K–$300K depending on public vs private. Retirement: 25× annual expenses (FIRE).