Use the free calculator, understand its assumptions and keep a copy of your result.
What can I use today?
Use Money Check-In, the Compound Interest Calculator, and the expanded calculator collection for budget, retirement, debt payoff, home and car costs, financial-picture scenarios and research. The free downloads remain available.
How do I read the calculator?
- Starting amount: the money in the example at the beginning.
- Monthly contribution: money added at the end of each month.
- Annual rate: a hypothetical nominal annual rate divided by 12 for monthly compounding.
- Years: the length of the illustration. Both scenarios use this same time period.
- Growth chart: solid lines show projected balances; dashed lines show money contributed. The gap is modeled growth or loss. Exact annual amounts appear in the table.
- Compare a second scenario: change the starting balance, monthly contribution or assumed rate for Scenario B. The comparison shows B minus A, so differences can reflect changed savings as well as changed returns.
The model uses a constant rate. It does not include taxes, fees, inflation or changes in market value. A calculated balance is an illustration, not a forecast or guaranteed return.
Why did the results change or disappear?
Changing an input makes the previous calculation out of date. Complete the highlighted fields and calculate again before exporting. Enter 0 when an amount is actually zero; leave an unknown value for later rather than treating it as zero.
How do I keep a copy?
The Compound Interest Calculator offers CSV and a printable summary of results, plus Save inputs JSON to continue later. The JSON file saves inputs, not calculated results. Open Restore saved inputs, review the file or pasted JSON, select Apply reviewed inputs, then select Calculate. Applying replaces the current inputs; reviewing alone does not. In the expanded collection, each tool lists its supported formats: JSON records, CSV tables or editable XLSX workbooks. Exports use current valid inputs; downloaded copies do not update automatically.
Debt Payoff can reopen its own JSON files, validate assumptions and recalculate both schedules. Budget JSON restores budget inputs only, not retirement assumptions. Valuation Snapshots reopens its own JSON records. Check each tool’s restore instructions before assuming it can reopen an export. Keep files privately and check the restored entries before relying on them.
The retirement website and exact-results CSV share the exact calculation. Its editable XLSX workbook calculates separately and can differ at rounding boundaries or very large amounts; keep the CSV when you need a record of the website result.
Where do my entries go?
Calculator entries are processed in your browser and are not submitted to DTP. There is no financial-account connection or cloud plan to create. Your browser may retain form values, so use care on a shared device. Ordinary website requests still reach hosting services; see Privacy & Data Handling.
How do the free PDFs work?
Download a blank file from Free Downloads. Print it or complete supported fillable fields in a compatible PDF viewer, then save a working copy on your own device. Reopen the saved copy to check it before relying on it. Keep sensitive completed pages somewhere appropriate for their contents. Each current free PDF includes a separate use-notice page. Personal printing, completion and private backups are allowed; see Copyright & Reuse for sharing and redistribution permissions.
Can I use the website offline?
Open the calculator collection’s Install & offline tools section while connected to optionally download its public tools. Offline support is limited to that collection; it does not download the whole WordPress website or save your financial inputs. Files from the former tools address remain on your device; use supported JSON restore here. Favorites and offline downloads must be set up again on this domain.
What if I find a problem?
Use Report a Bug or Share Feedback and include the tool name, your browser, the steps to reproduce the issue and the error message. Use fictional numbers. Please omit account numbers, passwords and private financial or household files.
Updated October 29, 2026. Educational estimates and general information. See Editorial Standards.