savings calculator

Savings Calculator

The Savings Calculator estimates how an initial deposit plus annual and monthly contributions could build under one fixed interest-rate assumption. It supports yearly contribution increases, several compounding frequencies, and a user-entered tax-rate drag so you can see the ending balance, total contributions, credited interest, and estimated tax paid.

Result

Ending balance: $92,116.99
Initial deposit: $20,000.00
Total contributions: $57,319.40
Total interest earned: $14,797.59
Estimated tax paid: $0.00
What this means: Estimate assumes end-of-period contributions and a fixed interest rate.

Scenario nameNotes

Save this result, then use saved scenarios to switch between assumptions.

Before you calculate

Use this calculator when deposits can grow over time, when annual and monthly contributions both matter, or when you want to test a flat tax-rate assumption. Use the regular savings interest calculator for a simpler fixed monthly-deposit model, the interest calculator when contribution timing or inflation adjustment matters, the compound interest calculator for principal-only growth, and the CD calculator for fixed-term deposit examples.

Formula summary

The calculator converts the nominal annual interest rate into an effective monthly rate from the selected compounding frequency. Continuous compounding uses e^(rate / 12) - 1. Each month, the balance earns gross interest, the entered tax rate reduces the credited interest, the monthly contribution is added after interest, and an annual contribution is added at the end of each twelfth month. Monthly and annual contributions increase by their entered yearly percentages at each savings-year boundary.

Worked example

Example: $20,000 plus growing annual deposits for 10 years

With the default inputs, a $20,000 initial deposit, $5,000 annual contribution growing by 3 percent per year, no monthly contribution, 3 percent interest compounded annually, 10 years, and 0 percent tax produce an ending balance of $92,116.99. Total contributions after the initial deposit are $57,319.40, and credited interest is $14,797.59. A taxed monthly-contribution example with $5,000 initially, $250 monthly growing by 2 percent per year, 4 percent monthly compounding, 5 years, and 20 percent tax produces about $22,751.00 ending balance, $15,612.12 contributions, $2,138.88 credited interest, and $534.72 estimated tax paid.

The result explains one fixed-rate deposit schedule. It is not an APY or AER disclosure, savings-account quote, tax calculation, product comparison, or recommendation about where to save.

Assumptions

Initial deposit, annual contribution, monthly contribution, contribution-increase rates, interest rate, compounding frequency, years, and tax rate follow the values entered on the page for the whole projection.
Contributions are modeled at period end: monthly deposits are added after that month's interest step, and annual deposits are added after every twelfth month. The calculator does not model beginning-period deposits, skipped deposits, withdrawals, or changing deposit schedules beyond the entered yearly increases.
The tax rate is a flat user-entered assumption applied to monthly interest. The calculator does not look up official tax rules, allowances, CPI data, live APY or AER, provider rates, account fees, deposit insurance, withdrawal rules, promotional terms, product limits, or personal tax treatment, and results remain educational estimates rather than financial, tax, legal, lending, investment, provider, or regulated advice.

Common mistakes to avoid

Treating Total interest earned as gross interest. In this calculator it is the interest credited after the entered tax-rate assumption; Estimated tax paid is tracked separately.
Comparing savings accounts from the result without checking whether a provider quotes APY, AER, gross rate, net rate, variable rate, bonus conditions, withdrawal limits, deposit caps, fees, or tax wrapper rules.
Assuming the contribution-increase fields add a one-time increase. They are yearly growth assumptions used when the model reaches a new savings year.

Methodology and sources

This calculator is an original implementation based on documented formulas, app-specific assumptions, deterministic fixtures, edge cases, rounding policy tests, and internal validation. It is not copied from a single source.

Outputs are checked with deterministic fixtures, edge cases, rounding policy tests, and internal independent comparator checks where overlapping outputs are available. The result remains an educational estimate, not a quote, approval, tax answer, or personalised advice.

Formula version 2026.05.22-generic-savings-growth-simulation. The version marks the calculation logic and validation fixture set used for this estimate.

CFPB Regulation DD Appendix A should be used before copy discusses US annual percentage yield disclosure calculations, advertised APY terminology, bonuses, fees, average daily balance methods, or product-specific account-yield claims.
IRS Topic 403 and relevant state tax-authority materials should be used before copy discusses US taxable interest, reporting, withholding, tax-exempt interest, state tax, or personal tax outcomes.
GOV.UK Tax on savings interest, HMRC materials, and relevant UK tax guidance should be used before copy discusses Personal Savings Allowance, starting rate for savings, ISA treatment, joint-account interest, foreign savings, or UK tax payment rules.
FCA, MoneyHelper, provider disclosures, FDIC, FSCS, bank terms, BLS, ONS, and relevant local regulators should be used before copy discusses AER, gross or net savings rates, variable rates, promotional rates, account protection, eligibility, withdrawal limits, deposit caps, inflation, provider comparisons, or jurisdiction-specific product claims.

Estimate only

The result is educational and is not financial, tax, legal, lending, investment, or regulated advice. Real provider terms, fees, rates, taxes, and personal circumstances can change the final answer.

Formula and help: read the full savings calculator methodology notes.