Recurring Compound Interest Calculator
Enter a starting balance, recurring contribution, frequency, term and assumed annual return to update the balance breakdown, chart and projection schedule instantly.
Inputs
Enter values to calculate automatically.
Advanced assumptions
Enter values to calculate automatically.
Results
- Total contributions
- —
- Pre-tax gain or loss
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- After-tax estimate
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- Inflation-adjusted value
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- Target timing
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Balance and contributions
Projection schedule
| Point | Period contributions | Period gain or loss | Ending balance |
|---|---|---|---|
| Enter values to calculate automatically. | |||
Return, tax and inflation rates are user assumptions, not guarantees or statements of local law. Check product fees, tax treatment and compounding rules. Daily mode uses a simple 365-day year.
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- Results firstPut the main number up front and keep the process secondary.
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How to separate contributions from compound growth
Compound growth applies each period’s return to the starting money and gains already in the balance. Recurring contributions join the balance when they are deposited and participate for the remaining term.
The return, tax and inflation rates here are user assumptions. Product fees, account rules, taxes and compounding dates vary, so treat the output as a scenario rather than a promise.
Separate the starting balance and recurring deposits
The starting balance is present on day one. A recurring contribution is added each selected period, so later deposits have less time to compound.
Read total contributions beside the ending balance to avoid calling all growth an investment return.
- Starting balance
- Contribution per period
- Total contributions
- Pre-tax gain or loss
Convert the nominal annual return to each period
Monthly mode divides the annual assumption by 12, while daily mode divides it by 365. This simple nominal conversion can differ from an effective annual yield or a product disclosure.
Use several return assumptions because none is guaranteed.
- Monthly rate = annual rate ÷ 12
- Daily rate = annual rate ÷ 365
- Daily model assumes 365 days
Choose when each contribution enters
Start timing adds the contribution before applying the periodic return. End timing applies the return first and then adds the contribution.
The gap can compound over long terms, so choose the setting closest to the actual deposit schedule.
- Start: contribute, then grow
- End: grow, then contribute
Read balance, contributions and gain together
The projected ending balance is before the tax assumption. Total contributions combine the initial balance and every deposit; their difference is pre-tax gain or loss.
Negative scenarios can end below total contributions.
- Ending balance
- Total contributions
- Pre-tax gain or loss
Treat tax as an explicit user assumption
The engine applies the entered tax rate only to positive cumulative gains. A 0% default does not mean the account is tax-free or that US rules have been applied.
Capital gains, interest, retirement accounts, withholding, loss offsets and timing can follow different rules.
- Identify account and product
- Enter a jurisdiction-specific rate
- Check the taxable event
Use inflation as a purchasing-power lens
The calculator discounts the after-tax estimate using the inflation rate entered for each period. A growing nominal balance may have slower real growth.
Personal spending patterns can differ from published inflation measures, so compare more than one assumption.
- Nominal balance
- After-tax estimate
- Inflation-adjusted value
Find the first period that reaches a goal
When a target is supplied, the engine finds the first pre-tax balance at or above it. A miss means the target was not reached inside the chosen term.
This is not a guaranteed date because it assumes the same contribution and return continue.
- Set a target
- Review first hit
- Compare missed scenarios
A $10,000 start with $300 per month
A $10,000 starting balance, $300 monthly contribution, ten-year term and 5% annual assumption create 120 monthly periods. Start timing lets each deposit earn that month’s return.
The 0% tax and 2% inflation defaults are scenario inputs to review, not legal or economic forecasts.
- $10,000 starting balance
- $300 per month
- 10 years
- 5% assumed annual return
Test 0% and negative-return boundaries
At 0%, the ending balance equals the starting balance plus all contributions. With a negative rate, continued saving may still end below total contributions.
Compare conservative, baseline and optimistic inputs instead of relying on one straight-line forecast.
- 0% baseline
- Negative stress case
- Positive scenario
Pair explanatory sources with product documents
SEC Investor.gov frames starting investment, recurring contributions, time and estimated return as core compound-interest inputs. CFPB explains interest earned on principal and accumulated interest.
Those sources explain the concept; they do not set the return, fees, taxes or rules for your product. Use the account agreement and applicable guidance.
- Concept: SEC and CFPB
- Product: disclosures and agreement
- Tax: applicable jurisdiction
Compound interest calculator questions
QWhat does this compound interest calculator project?
It uses a starting balance, recurring contribution, frequency, term and assumed annual return to project a pre-tax balance, contributions, gain or loss, an after-tax example, real value and target timing.
QHow do monthly and daily modes differ?
Monthly mode divides the nominal annual return by 12. Daily mode divides it by 365 and converts months using a rounded 365/12 assumption.
QWhy does contribution timing matter?
A start-of-period contribution earns the same period’s return. An end-of-period contribution is added after that return, so the start setting can finish slightly higher.
QDoes the 0% tax default represent US tax law?
No. It is an empty tax assumption. Enter a rate appropriate to the account, product, jurisdiction and taxable event you are modeling.
QCan I use zero or negative returns?
Yes. At 0%, only contributions accumulate. A negative return can reduce the balance, and the tool does not subtract the tax example unless cumulative gains are positive.
QWhat is the inflation-adjusted value?
It discounts the after-tax estimate by the inflation rate you entered to show an illustrative purchasing-power value. It is not an inflation forecast.
QHow is the target date determined?
The calculator finds the first period when the pre-tax balance reaches the target. It reports a miss when the target is not reached within the selected term.
QWhy can a real account produce a different result?
Fees, trading days, deposit timing, taxes, rounding and product compounding rules vary. Every rate on this page is a user assumption.
Explanatory sources
Checked August 10, 2026. The explanations use SEC Investor.gov and CFPB compound-interest resources. Return, tax and inflation inputs remain user assumptions, and product rules vary.