Compound interest with increasing contributions calculator
Model growth with periodic contributions and annual increases.
Your inputs
Your results
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Compare two scenarios.
Run the tool, then save A or B to compare headline results and entered values. Keep currencies, periods and assumptions consistent.
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Run the tool to save your first scenario.
How it works
Project a balance with end-of-month contributions that increase once each year. Convert the assumed effective annual return to an equivalent monthly rate.
Read the source reference ↗A few things to know
Constant hypothetical return, no volatility, taxes or fees. Negative returns are allowed down to -50%. Contribution increases are assumptions, not promises. Calculations are bounded to prevent overflow.
Results use your inputs. Keep all money amounts in the same currency.
When to use this tool
Model regular saving with a deliberate annual increase. Keep contribution growth separate from investment return so the source of balance growth is clear.
- Model rising contributions.
- Compare saving assumptions.
- Separate contributions from modeled growth.
How to use compound interest with increasing contributions calculator
Prepare the inputs
Use balances and rates from current statements, in one currency.
Choose the settings
Enter the scenario assumptions; this tool does not fetch market rates.
Review and export
Compare the report with the actual account terms before acting.
Try the supplied example
Inputs
initial: 10000; monthly: 200; return: 5; increase: 3; years: 20
Result
The example starts at 10,000 and adds 200 per month, increasing contributions by 3% each year.
What it means
The fixed 5% return is a scenario, not a forecast.
Common mistakes to avoid
Contribution growth is not investment return
Contribution growth is not investment return.
A smooth projection hides market volatility
A smooth projection hides market volatility.
Frequently asked questions
Definitions, edge cases, and practical next steps for this tool. Search all tool FAQs ↗
When are contributions added?
At the end of each month, after that month’s modeled growth.
When do contributions increase?
At the first month of each new modeled year.
Is the return nominal APR?
No. It is an effective annual return converted to a matching monthly growth rate.
Can returns be negative?
Yes, down to -50% annually.
Are taxes or fees included?
No. Use the separate fee comparison and account for tax rules independently.
Is a steady return realistic?
Actual returns vary; this fixed-return model only illustrates assumptions.
Are my inputs uploaded or stored?
Processing happens locally in your browser. This tool does not upload inputs. Downloads stay on your device; sharing or opening them in another service is your choice.
What should I check before using the output?
Constant hypothetical return, no volatility, taxes or fees. Negative returns are allowed down to -50%. Contribution increases are assumptions, not promises. Calculations are bounded to prevent overflow.
Explore the topic in the blog
Sources and method
Use the references below to check definitions and platform guidance. The model’s scope and limits are explained above. Read our editorial standards.