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Retirement Savings Calculator

Projects retirement savings from the current balance and a fixed monthly contribution compounded monthly at an assumed annual return until the retirement age, reports the result in today's money using an inflation rate, and the income it supports at a 4 % withdrawal rate.

When to use

You want to estimate what your savings will grow to by retirement, how much of that is contributions versus growth, and what it is worth in today's purchasing power.

Do not use when: You need the amount required to retire (use fire-number), how long a balance lasts in retirement (use savings-withdrawal), or contributions that change over time.

Formula

i = annual_return_percent/1200; m = 12 × (retirement_age − current_age); balance = current_savings × (1 + i)^m + monthly_contribution × ((1 + i)^m − 1) / i; todays_money = balance / (1 + inflation/100)^years; income = 0.04 × balance

Constant return, constant contribution, end-of-month deposits, no taxes or fees. Real returns vary; the 4 % withdrawal figure is the Trinity-study rule of thumb for a 30-year retirement, not a guarantee.

Inputs

ParameterTypeUnitRequiredDescription
current_agenumberyearsyesAge today. Range: ≥ 0, ≤ 100
retirement_agenumberyearsyesPlanned retirement age; must exceed current_age. Range: > 0, ≤ 110
current_savingsnumberdefault 0Retirement balance today. Range: ≥ 0, ≤ 1000000000000
monthly_contributionnumberdefault 0Amount added at the end of every month (including any employer match). Range: ≥ 0, ≤ 1000000000
annual_return_percentnumber%default 7Expected nominal annual return in percent, compounded monthly. Range: ≥ -50, ≤ 50
annual_inflation_percentnumber%default 2.5Assumed annual inflation used to express the result in today's money. Range: ≥ -10, ≤ 30

Outputs

OutputTypeUnitDescription
years_to_retirementnumberyearsretirement_age − current_age.
balance_at_retirementnumberProjected balance in future currency.
balance_in_todays_moneynumberbalance_at_retirement / (1 + inflation)^years.
total_contributionsnumbercurrent_savings + monthly_contribution × months.
investment_growthnumberbalance_at_retirement − total_contributions.
annual_income_at_4_percentnumber0.04 × balance_at_retirement (nominal).
annual_income_in_todays_moneynumber0.04 × balance_in_todays_money.

Example

Age 30 to 65, 50,000 saved, 500/month, 7 %, 2.5 % inflation: {"current_age":30,"retirement_age":65,"current_savings":50000,"monthly_contribution":500,"annual_return_percent":7,"annual_inflation_percent":2.5} → {"years_to_retirement":35,"balance_at_retirement":1475834.89,"balance_in_todays_money":621874.12,"total_contributions":260000,"investment_growth":1215834.89,"annual_income_at_4_percent":59033.4,"annual_income_in_todays_money":24874.96}

Age 45 to 67, 200,000 saved, 1,000/month, 6 %, 3 % inflation: {"current_age":45,"retirement_age":67,"current_savings":200000,"monthly_contribution":1000,"annual_return_percent":6,"annual_inflation_percent":3} → {"years_to_retirement":22,"balance_at_retirement":1292451.73,"balance_in_todays_money":674520.87,"total_contributions":464000}

GET https://tttkmbb.com/api/v1/calculate/retirement-savings?current_age=30&retirement_age=65&current_savings=50000&monthly_contribution=500&annual_return_percent=7&annual_inflation_percent=2.5

Machine access

Sources

FAQ

Why is the inflation-adjusted balance so much lower?

At 2.5 % inflation prices rise 2.37× over 35 years, so 1.48 million then buys what about 622,000 buys today. Plan with the today's-money figure.

Should I enter a nominal or real return?

Enter the nominal return and let the inflation input do the adjustment. Entering a real return with inflation set to 0 gives the same today's-money result.

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