Fidamen

Savings Bond Calculator

This calculator estimates the current redemption value and accrued interest for U.S. savings bonds based on user-supplied dates, purchase amount, and an annual rate. It provides multiple workflows: Series I (use composite annual rate) and Series EE (use stated annual yield or an optional guaranteed doubling rule where applicable).

Results are estimates produced by compounding the supplied annual rate monthly and do not automatically fetch official published rates. Use official published rates and exact redemption schedules when making legal or tax decisions.

Updated Nov 20, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record a4212f1f93fb • Reviewed by Fidamen Standards Committee

Estimate value using a user-supplied annual composite rate (enter the current published composite annual rate as a percent). This method compounds monthly.

Inputs

Advanced inputs

EE bond special options

Results

Updates as you type

Estimated current value

$64.79

Accrued interest

$14.79

Months since issue

311

OutputValueUnit
Estimated current value$64.79USD
Accrued interest$14.79USD
Months since issue311months
Primary result$64.79

Visualization

Methodology

The tool treats the provided annual rate as an effective nominal annual rate and converts it to a monthly rate for compounding: monthly_rate = annual_rate / 12. The valuation period is the month difference between issue and redemption dates. The calculator compounds monthly for the estimated future value.

For Series I, users should supply the composite annual rate (published as a percentage) if they want an estimate that reflects the published composite. For Series EE, users may supply the bond's stated annual yield or enable the guaranteed doubling option (where the bond's program rule guarantees a specific outcome).

All model decisions, rounding behavior, and inputs should be validated against official documentation before use in compliance reporting or tax filings. This tool follows quality and accuracy practices inspired by ISO 9001 (quality management), NIST guidance for data integrity, and general numerical precision recommendations from IEEE.

Key takeaways

This calculator is a practical estimator for bond value and accrued interest using user-supplied rates and dates. It supports multiple workflows and provides transparent assumptions.

For legally binding valuations or tax reporting, always verify with official documentation and published rates.

F.A.Q.

Does this calculator use official published Treasury rates automatically?

No. The calculator requires you to enter an annual rate or composite rate. It does not fetch official published rates. Always cross-check results with official rate publications for precise redemptions.

Why does the tool compound monthly?

Monthly compounding is used here as a consistent, conservative estimate for accrual over fractions of a year. Actual accrual rules for specific bond issues may use semi-annual or other accrual conventions; consult official bond documentation for exact treatments.

How accurate are the results?

Results are estimates intended for planning. They follow numerical best practices but do not replace official redemption calculations. See the accuracy & compliance note below for standards and limits.

What should I enter for the annual rate field?

Enter the bond's annual yield or, for Series I, the composite annual rate (expressed as a percentage). If unsure, use the official published composite or yield for the relevant issue date.

Sources & citations

Further resources

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: a4212f1f93fb

What changed (latest)

v1.0.0 • 2025-11-20 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

UI

v1.0.0

Governance

Last updated: Nov 20, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

  • MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
  • MINOR: New features or fields that do not change existing outputs for the same inputs.
  • PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

  • Verify formulas and unit definitions against primary standards or datasets.
  • Run golden-case regression suite and edge-case suite.
  • Record reviewer sign-off with credentials and scope.
  • Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

  • Uses exact unit definitions from the Fidamen conversion library.
  • Internal calculations use double precision; display rounding follows the unit's configured decimal places.
  • Not a substitute for calibrated instruments in regulated contexts.
  • Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-20 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 8e61022d92f3