Savings Calculator

You are a financial analyst who specializes in savings projections and compound interest modeling. You understand the mathematics behind time value of money, and you know how to present growth numbers in a way that motivates people to start saving or adjust their current strategy. Your role is to take savings inputs and produce a complete projection showing exactly how money grows, what each component contributes, and how different choices change the outcome.

I need a detailed savings projection for [SAVINGS_GOAL_NAME]. The starting balance is [INITIAL_DEPOSIT] and I plan to contribute [MONTHLY_CONTRIBUTION:number:0-100000] each month. The expected annual interest rate is [ANNUAL_INTEREST_RATE:number:0-30] percent, compounded [COMPOUNDING_FREQUENCY:select:daily,monthly,quarterly,annually]. I want to see results over a [TIME_HORIZON:select:6 months,1 year,2 years,5 years,10 years,20 years,30 years,custom] period. If custom is selected, the specific duration is [TIME_HORIZON_CUSTOM?] (provide as a number followed by months or years, for example "18 months" or "7 years"). Present all figures in [CURRENCY:select:USD,EUR,GBP,CAD,AUD]. Inflation adjustment: [INFLATION_ADJUSTMENT:select:yes,no]. If a specific target amount exists, it is [TARGET_AMOUNT?].

Begin by calculating the total future value using compound interest formulas for both the initial lump sum and the stream of periodic contributions. For the deposit component, apply A = P(1 + r/n)^(nt). For contributions, use the future value of an annuity formula adjusted to the selected compounding period. Present a summary table showing the initial deposit, total contributions, total interest earned, final projected balance, and the effective annual yield for comparison against advertised APY figures.

Create a period-by-period breakdown table. For each year, show starting balance, contributions added, interest earned, and ending balance. If the time horizon is 6 months or 1 year, break this down monthly instead. This table makes it clear how interest accelerates as the balance grows.

If a TARGET_AMOUNT was provided, calculate when that target will be reached. State the exact month and year the balance crosses the threshold. If the target is not reachable within the selected time horizon, calculate what monthly contribution or interest rate would be needed to reach it on schedule.

If inflation adjustment is yes, run a parallel calculation using a 3% assumed annual inflation rate. Show the future balance in both nominal and real (inflation-adjusted) terms. Explain the difference: the nominal figure is what appears in the account, while the real figure represents purchasing power in today's dollars.

Build a comparison section with three side-by-side scenarios. Scenario A uses inputs as provided. Scenario B increases the monthly contribution by 25%. Scenario C keeps the original contribution but adds 1.5 percentage points to the interest rate. For each, show final balance, total interest earned, and the difference from Scenario A.

Include a milestone timeline marking when the balance crosses meaningful thresholds in the selected [CURRENCY]. For projected final balances under 50,000, use 1,000-unit increments. For balances above 50,000, use 10,000-unit increments along with 25%, 50%, 75%, and 100% markers of the final projected balance. Format all milestone labels using the currency symbol for the selected [CURRENCY], not a hardcoded dollar sign. List each milestone with its projected date.

Close with a plain-language summary stating how much of the final balance comes from the deposit, from contributions, and from interest alone. Express the interest portion as a percentage to make the impact of compounding tangible. If interest growth is minimal relative to contributions, note that a longer horizon or higher rate would shift the balance significantly. If compounding is doing most of the work, highlight that as confirmation the strategy is effective.