# Savings account comparison calculator - Human page: https://happytails.ai/en/finance-tools/savings-account-comparison-calculator/ - Markdown: https://happytails.ai/en/finance-tools/savings-account-comparison-calculator.md - Structured JSON: https://happytails.ai/agents/en/finance-tools/savings-account-comparison-calculator/index.json - Visibility: public ## Tool capabilities | Property | Value | | --- | --- | | Tool ID | `savings-account-comparison-calculator` | | Category | finance-tools | | Implementation | Registered implementation. Registration alone is not a production-quality guarantee. | | Browser execution | Use the visible action or interactive controls. | | Browser processing | Browser; see tool notes for network behavior. | | HTTP API | Not callable through HTTP. | | Browser-agent interface | run_current_tool | ### Implementation notes Compared on your device for up to 10 accounts over at most 600 months. ### Inputs and settings Text input: Account rows. Example or placeholder shown in the interface (not a validated fixture): ```text account,rate,credit,monthly_fee,annual_fee,opening ``` One account per line: name, yearly rate in percent, credit frequency, monthly fee, annual fee and an optional opening deposit. Up to 10,000 characters. Review the settings before running. | Setting | Meaning | Control type | Default | Constraints | | --- | --- | --- | --- | --- | | `months` | Months to compare | text | "60" | | | `opening` | Opening deposit | text | "1000" | | | `contribution` | Monthly contribution | text | "200" | | | `timing` | Contribution timing | select | "end" | Allowed: end, start | | `contributionIncrease` | Yearly contribution increase (%) | text | "0" | | | `decimals` | Decimal places in amounts | select | "2" | Allowed: 2, 0, 1, 3, 4, 5, 6 | ### Browser-agent workflow 1. Open the human page in a browser that supports WebMCP. 2. Discover the interface exposed by that page; use its actual schema. 3. Select files on the page first when the tool requires files. 4. Call `run_current_tool` with valid input and settings. 5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links. Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution. ### Planning specification 1 to 10 accounts in at most 10000 characters, rates from 0 to 100 percent, 1 to 600 months, yearly contribution increases from 0 to 100 percent and amounts up to 1000000000000 at 0 to 3 decimal places, 100000000000 at 4, 10000000000 at 5 and 1000000000 at 6, with every month-end balance within 1000000000000000 minor currency units (10000000000000 at 2 decimal places). Calculated locally in your browser. Downloads are a JSON report, a ranking CSV and a CSV of monthly ledgers for every account. This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support. ### Complete machine-readable capability record ```json { "id": "savings-account-comparison-calculator", "category": "finance-tools", "built": true, "requirements": "1 to 10 accounts in at most 10000 characters, rates from 0 to 100 percent, 1 to 600 months, yearly contribution increases from 0 to 100 percent and amounts up to 1000000000000 at 0 to 3 decimal places, 100000000000 at 4, 10000000000 at 5 and 1000000000 at 6, with every month-end balance within 1000000000000000 minor currency units (10000000000000 at 2 decimal places). Calculated locally in your browser. Downloads are a JSON report, a ranking CSV and a CSV of monthly ledgers for every account.", "implementation": { "fields": [ { "key": "months", "label": "Months to compare", "value": "60", "type": "text", "maxLength": 10, "help": "Whole months from 1 to 600." }, { "key": "opening", "label": "Opening deposit", "value": "1000", "type": "text", "maxLength": 30, "help": "Used for every account whose opening cell is blank." }, { "key": "contribution", "label": "Monthly contribution", "value": "200", "type": "text", "maxLength": 30, "help": "Added to every account each month. Enter 0 for none." }, { "key": "timing", "label": "Contribution timing", "value": "end", "type": "select", "values": [ "end", "start" ], "labels": { "end": "End of each month", "start": "Start of each month" } }, { "key": "contributionIncrease", "label": "Yearly contribution increase (%)", "value": "0", "type": "text", "maxLength": 20, "help": "From 0 to 100, applied every 12 months." }, { "key": "decimals", "label": "Decimal places in amounts", "value": "2", "type": "select", "values": [ "2", "0", "1", "3", "4", "5", "6" ] } ], "registrationFamily": "personal-balance-schedules", "inputMaxLength": 10000, "inputErrorCode": "PERSONAL_BALANCE_SCHEDULES_TOO_LONG_ACCOUNTS", "note": "Compared on your device for up to 10 accounts over at most 600 months.", "experience": { "automatic": false, "single": false, "inputMaxLength": 10000, "inputMode": "text", "label": "Account rows", "placeholder": "account,rate,credit,monthly_fee,annual_fee,opening", "help": "One account per line: name, yearly rate in percent, credit frequency, monthly fee, annual fee and an optional opening deposit. Up to 10,000 characters. Review the settings before running.", "action": null }, "mode": "explicit", "interactive": false }, "execution": "Browser interface", "api": null, "browser_agent": { "supported": true, "name": "run_current_tool", "discovery": "WebMCP on the human page in a supporting browser", "verification": "See audit/API-AUDIT.md; availability is not verification" } } ``` ## Page guide Compare up to 10 savings accounts with their own rates, crediting frequency, fees and opening deposits under the same monthly contribution. See the closing balance, interest and fees for each account, ranked from best to worst. How can we improve this tool? Report a problem or share an idea. Please leave out private information. Your message and the tool name go to our team via PostHog. ### How to use Savings account comparison calculator 1. Paste one account per line under the header account,rate,credit,monthly\_fee,annual\_fee,opening. 2. Enter how many months to compare, the opening deposit for accounts without one and the monthly contribution. 3. Choose when contributions arrive and any yearly increase. 4. Review the ranking, then download the JSON report, the ranking CSV or the monthly ledgers CSV. ## Useful next steps - [Compound interest](https://happytails.ai/en/finance-tools/compound-interest/) ([Markdown](https://happytails.ai/en/finance-tools/compound-interest.md)) - [Savings goal](https://happytails.ai/en/finance-tools/savings-goal/) ([Markdown](https://happytails.ai/en/finance-tools/savings-goal.md)) - [Simple interest calculator](https://happytails.ai/en/finance-tools/simple-interest/) ([Markdown](https://happytails.ai/en/finance-tools/simple-interest.md)) ## Method Each account runs a monthly ledger. Interest accrues every month on the balance at the yearly rate divided by 12, rounded to the cent, and is added to the balance at the end of every credit period (monthly, quarterly, semiannual or annual) and in the last month. Contributions arrive at the start or end of each month, monthly fees come out every month and annual fees every 12 months. Banks state yields as an annual percentage yield under Regulation DD, 12 CFR part 1030, appendix A (Consumer Financial Protection Bureau, checked 16 October 2026); this tool does not compute that disclosure, it projects balances from the rates you enter. ### Ranking Accounts are ranked by closing balance after fees. Equal balances share a rank, and the report shows how far each account is behind the best one. ### Assumptions and limits Rates stay the same for the whole period. Tiered rates, bonus rates, daily balance methods and taxes are not modelled. A blank credit cell means monthly and a blank opening cell uses the shared opening deposit. Every row needs as many cells as the header, so keep the comma of an empty cell. Fees never take the balance below zero. This is a calculation from your own numbers, not financial advice.