Annuity Calculator

Introduction

This Annuity Calculator projects how money grows when you start with a lump sum and add the same amount every month for a fixed number of years at a steady return. It is aimed at accumulation phase planning: building a balance inside a deferred annuity, taxable investment account, or any vehicle where you make level periodic contributions. Enter starting balance, monthly payment, annual return, and years. The output shows ending value, total contributed, and interest earned. It does not price insurance company annuity contracts with riders or surrender charges.

Who this calculator is for

Savers setting up automatic monthly transfers who want to see the future value of discipline plus compounding. It fits someone comparing bank CD laddering against steady mutual fund contributions, or evaluating whether to fund a deferred annuity with $400 per month on top of an existing balance. Small business owners building a cash reserve before a large equipment purchase also use it to pick a horizon that matches the purchase date.

If you already have a large balance and need sustainable withdrawals in retirement, use the Annuity Payout Calculator instead. For employer match and deferral math, use the 401(k) Calculator. Tax-advantaged IRA growth belongs in the IRA Calculator when you compare account types.

What it estimates

The engine uses future value of a lump sum plus future value of an ordinary annuity: payments at period end unless the form states otherwise. Each month or year, interest applies to the opening balance including prior contributions. Total contributed equals initial deposit plus all payments. Interest earned is ending balance minus total contributed.

Fixed return assumptions smooth volatile markets. Variable annuities and indexed annuities with caps and floors are not replicated by a single rate. Insurance fees, mortality and expense charges, and bonus credits are omitted. For open-ended savings with a goal date, the Savings Calculator solves required payment instead of ending balance.

Inputs explained

Keep units consistent: monthly payments pair with monthly compounding or an equivalent effective annual rate as labeled on the form.

• Initial deposit: Lump sum already in the account on day one.
• Monthly contribution: Fixed amount added each month for the full term.
• Annual return: Expected average growth rate before taxes and fees.
• Term in years: Length of accumulation period until you stop adding or start withdrawals.
• Compounding frequency (if shown): Monthly or annual; affects small differences in ending balance.

How to read the results

Ending balance is the projected account total at the end of the term. Early in the schedule, contributions make up most of the balance; later, interest dominates if return is positive. A table by year helps you see when the account crosses milestones you care about, such as $100,000 or a down payment target.

If you lower return by one point and the goal still clears, the plan has margin. If one point lower misses the goal, increase payment or extend the term and recalculate once. Do not chase return assumptions to make the chart look better.

Worked example

Initial deposit $75,000, monthly contribution $400, annual return 5%, term 12 years. Total payments over 12 years: $75,000 plus $57,600 of contributions equals $132,600 contributed. At 5% compounded monthly, ending balance lands near $195,000 to $200,000 with interest earned about $65,000 to $68,000.

Drop monthly contribution to $0 and the $75,000 alone grows to roughly $135,000 at 5% over 12 years. The $400 per month adds about $60,000 to $65,000 of ending value beyond that baseline, showing that steady additions matter even when the starting balance is already large. Raise return to 7% and ending balance jumps toward $230,000, illustrating sensitivity without guaranteeing market outcomes.

Practical use cases

Funding a deferred annuity before converting to income at retirement. Modeling taxable brokerage auto-invest plans alongside maxed 401(k). Parents saving monthly in a UTMA or 529 while grandparents funded the opening deposit.

Compare 10-year versus 15-year terms for the same payment to see whether delaying the purchase goal reduces required monthly savings. Layer result into the Retirement Calculator as part of total nest egg if this account is for retirement.

Limitations and related tools

Surrender periods, partial withdrawals, tax on growth, and annuitization quotes from carriers are not included. Payments assumed constant; real life skips months or raises amounts. Negative returns in some years are not simulated unless you run separate scenarios.

Withdrawal phase: Annuity Payout Calculator. IRA tax wrapper: Roth IRA Calculator. Broader plan: Retirement Calculator. Read retirement savings by age for context.

How It Works

1. Enter starting balance. Type any lump sum already invested toward this goal.
2. Set monthly contribution. Enter the fixed amount you plan to add each month for the entire term.
3. Choose return and years. Pick annual return and accumulation years. Match compounding to the form labels.
4. Read ending balance and interest. Calculate and note total contributed versus interest. Adjust payment or term if the goal is short.

Formula and methodology

The Annuity Calculator uses this identity for the scenario you enter. A bank, payroll system, or tax program may round on a 360-day year or average daily balance, so a statement can differ by a small amount.