Accrued Interest Calculator

The calculator implements three methods so users can match the workflow used by an issuer or market practice: periodic bond coupon accrual (annual coupon × fraction of period), simple loan accrual (principal × annual rate × fraction of year), and a daily-rate method (annual rate / 365 × days).

Day-count conventions are implemented by a user-supplied denominator (commonly 360 or 365). Where exact legal definitions are required (for example, 30/360 variants or Actual/Actual ISMA), use a dedicated day-count conversion with calendar dates; this tool accepts days as input to keep the core arithmetic explicit and transparent.

Accuracy and numerical behavior follow best practices for reproducible finance calculations. For computational integrity and auditability, developers and integrators should follow guidance issued by standards organizations (NIST, ISO) and use appropriate numeric types (IEEE floating point vs decimal fixed-point) depending on rounding requirements.

Select the method that matches the instrument you are valuing (bond coupon vs loan vs daily accrual).

Provide days explicitly or compute them with a dedicated date-to-days helper that applies the exact legal day-count rule when necessary.

This tool performs arithmetic approximations; adopt fixed-point decimal arithmetic and institution-specific rounding when integrating into accounting or trading systems.

Bond example: Face Value 1,000, Coupon 6% annually, Days accrued 45, Denominator 360 → Accrued interest = 1000 × 0.06 × (45/360) = 7.50.

Loan example: Principal 5,000, Annual rate 4%, Days 30, Denominator 365 → Interest = 5000 × 0.04 × (30/365) ≈ 16.44.

Daily example: Principal 10,000, Annual rate 3%, Days 10 → Interest = 10000 × (0.03/365) × 10 ≈ 8.22.