Savings Calculator: Compound Growth and Recurring Deposits

We convert the annual rate to the effective monthly rate that compounds back to exactly the annual rate over 12 months, about 0.2466% a month for 3%, and apply it once per month to the balance at that point. Each month's interest is added to the balance before the next month's calculation, so you earn interest on previous interest as well as on your deposits. In the worked example of $5,000 starting balance plus $200 monthly deposits at 3% for 10 years, the first month alone adds $12.33 in interest before that month's $200 deposit lands, and that $12.33 keeps earning its own interest every month afterward. That snowball effect is why $29,000 paid in grows into an end balance of $34,609.18 after 10 years, rather than settling at contributions plus a flat, non-compounding return. Over a shorter 5-year horizon the same inputs grow to $18,712.56, only $1,712.56 above the $17,000 paid in, showing that most of the $5,609.18 in total growth accumulates in the second half of a 10-year plan.

You can choose daily, weekly, biweekly, semimonthly, monthly, quarterly, or annually, and the amount you enter is the amount of each deposit. Daily to monthly deposits are added up to one monthly amount booked at the end of each month, so $50 a week becomes $216.67 a month ($50 × 52 ÷ 12). Quarterly and annual deposits land in full at the end of each quarter or year: $500 per quarter means $2,000 a year, and with a $10,000 start at 2% for 10 years that plan reaches $34,252.95 on $20,000 of deposits.

The first increase applies in month 13 and then every 12 months. A percentage increase compounds on the previous year's deposit level, so a 5% annual raise on a $200/month deposit makes year 2 contributions $210, year 3 $220.50, and so on. A fixed increase is added to every deposit once a year: $50 a week rising by $10 a year means $60 a week in year 2 and $140 a week in year 10. With a $10,000 start at 2%, that plan pays in $49,400 over 10 years and ends at $65,837.54.

It is a percentage per period, applied after the base monthly rate on its own cadence: monthly, quarterly, or annually. Each payment is calculated on the balance at the start of that period and credited at its end, before that month's deposit. This lets you model savings products that pay a base rate every month and an additional bonus rate on a different schedule.

Cumulative growth is the total earned from both the base rate and any extra rate over the full savings horizon, before any taxes or fees. On the worked example of $5,000 plus $200/month at 3% for 10 years, cumulative growth is $5,609.18. Over a shorter 5-year horizon with the same $200 monthly deposit and 3% rate, cumulative growth totals only $1,712.56 on $17,000 paid in, so growth more than triples when the time horizon merely doubles from 5 to 10 years. This reflects how compounding rewards patience: growth accelerates faster than the contribution total because earlier interest keeps earning interest for longer. Raising the annual rate from 3% to 4% on the same $5,000 start and $200 monthly deposit over 10 years lifts cumulative growth to $7,740.41, about 38% more than the $5,609.18 baseline, because a higher rate compounds every month rather than adding a flat amount each year.

No. All outputs are nominal and do not account for inflation or tax. To approximate a real (inflation-adjusted) outcome, enter a rate equal to the nominal rate minus the expected inflation rate. To approximate an after-tax outcome, reduce the rate by your marginal tax rate on savings interest. For example, entering 1% instead of the worked example's 3% rate (approximating 3% nominal minus 2% expected inflation) produces a projected balance of $30,747.30 in today's purchasing power, well below the $34,609.18 nominal figure, which shows how much inflation can erode a decade of savings growth. Someone in a 25% marginal tax bracket on interest income could instead re-run the same scenario at about 2.25% (3% minus 25% of 3%) to estimate an after-tax balance. At that 2.25% after-tax rate the same $5,000 start and $200 monthly deposit reaches $33,100.74 after 10 years, $1,508.44 below the $34,609.18 pre-tax figure, showing how even a modest tax rate compounds into a real gap over a decade.

The starting amount is the lump sum already in your account on day one. Because it compounds for the entire savings horizon, every extra dollar in the starting amount earns more in total interest than the same dollar added as a late contribution. In the worked example, the $5,000 starting amount contributes $1,719.58 in growth over 10 years at 3%. Doubling the starting amount to $10,000 while keeping the 3% rate and 10-year horizon would also double that specific contribution to $3,439.16, because a lump sum's own growth scales linearly with its principal when the rate and timeframe stay fixed. Contributions added later in the plan do not get this same multiplier, since each deposit only compounds for the months remaining after it lands. Shortening the horizon to 5 years while keeping the same $5,000 start and 3% rate cuts that contribution to $796.37, less than half the 10-year figure, since a lump sum needs years left to compound.

The effective monthly rate is the monthly rate that compounds to exactly the annual rate over 12 months: (1 + annual rate) to the power 1/12, minus 1. For a 3% annual rate that is about 0.2466% per month, slightly less than 3% ÷ 12 = 0.25%. It is applied to the current balance each month, and twelve months of it grow a balance by exactly 3%, so the rate you enter works as the effective annual rate: the yearly return you actually earn before any extra rate. Using 0.25% a month instead would grow the balance by about 3.04% a year, computed as (1 + 0.0025) raised to the 12th power minus 1, and overstate the return. The gap widens as the rate rises: 4% becomes about 0.3274% a month, while the ÷ 12 shortcut would compound to about 4.07%. That is why a nominal rate credited monthly can look slightly better than the same rate quoted as an effective annual rate.

Not for daily, weekly, biweekly, semimonthly or monthly deposits: the calculator adds them up to one monthly amount booked at the end of each month, so $50 a week gives exactly the same result as $216.67 a month. In a real account weekly deposits start earning a few days sooner, a difference too small to change a long-term plan. Timing does matter for quarterly and annual deposits, which land in one go at the end of the period: see the next question.

In full at the end of the period: a quarterly deposit at the end of months 3, 6, 9 and 12, an annual deposit at the end of month 12. Money that arrives later earns less interest, so the same yearly total grows less when it is paid in fewer, later deposits. With a $10,000 start at 2% for 10 years, $2,000 a year ends at $34,289.41 when spread over 12 monthly deposits, $34,252.95 as $500 per quarter and $34,089.39 as one $2,000 deposit at the end of each year.

A higher deposit each year means a larger balance sooner, and that larger balance earns interest for all remaining years. The effect is multiplicative rather than additive: each extra euro deposited in year 3 earns compounding interest for 7 more years (in a 10-year plan), while the same euro deposited in year 9 only earns for 1 year.

The base rate is applied every single month to the current balance. The extra rate is applied on a separate schedule you choose: monthly, quarterly, or annually. Both rates are in addition to each other; you can set either to zero to isolate the effect of the other.

No. This savings calculator is for informational and planning purposes only and does not constitute financial, tax, legal or investment advice. Actual savings rates, account terms and tax treatment vary by provider and jurisdiction. Always consult a qualified financial adviser for decisions involving real savings products.