Description
Calculate simple or effective annual compound interest under a supplied ledger day-count basis.
Historical accounting and tax terms depend on period, rate and valuation conventions. Applying a supplied factor to a ledger amount differs from establishing which historical contract, calendar or tariff actually applied.
Calculate simple or effective annual compound interest under a supplied ledger day-count basis.
When to use this tool
Use Old Ledger Interest Period Factor when checking a declared historical interest or duty term.
How to use the tool and how it works
- Enter principal, ratePerYear, days, daysPerYear, compound. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read interest. Use the output convention below.
Require ratePerYear > -1, nonnegative days and positive daysPerYear. Interest is principal*ratePerYear*days/daysPerYear for simple interest, or principal*expm1(log1p(ratePerYear)*days/daysPerYear) when compound.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| principal | Principal | Required. Finite number. |
| ratePerYear | Rate Per Year | Required. Finite number; strictly above -1. |
| days | Days | Required. Finite number; minimum 0. |
| daysPerYear | Days Per Year | Required. Finite number; strictly above 0. |
| compound | Compound | Required. Boolean. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| interest | Interest | Required. Finite number. |
{
"input": {
"principal": 100,
"ratePerYear": 0.1,
"days": 180,
"daysPerYear": 360,
"compound": false
},
"output": {
"interest": 5
}
}Limitations and assumptions
- Rate is an annual effective fraction in compound mode. Principal may be signed; actual ledger calendars, contract conventions and historical interest rules are not inferred.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the relevant archival terms and legal context for actual ledger interpretation and obligations.
References
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