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Savings Bond Calculator

Future value of a US savings bond. Free online Savings Bond Calculator. Calculate savings bond online — fast, accurate, mobile-friendly, no signup needed.

Future value
$198.98

Derivation

  1. ├── 01GivenP = 100, r = 3.5, n = 20
  2. ├── 02Formulat × (1+a / 100)^(n)
  3. ├── 03Substitutet × (1+a / 100)^(20)
  4. └── 04Compute Future value$198.98
Did you know?

The US 401(k) exists because of a single 1978 tax-code subsection (section 401(k)) that accidentally allowed tax-deferred salary deferrals.

§01What is

Understanding the Savings Bond Calculator

The Savings Bond Calculator computes Future value from 3 inputs: purchase price ($), annual rate (%), years. Future value of a US savings bond.

Quick calculators for the math that shouldn’t need a notepad — instant, accurate, private to your browser. The Savings Bond Calculator sits in that toolkit — it future value of a US savings bond. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

t × (1+a / 100)^(n)

Where

P
Purchase price ($)
r
Annual rate (%)
n
Years
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Purchase price ($) = 100, Annual rate (%) = 3.5, Years = 20.

  1. 01Start by noting the input — Purchase price ($): 100.
  2. 02Start by noting the input — Annual rate (%): 3.5.
  3. 03Start by noting the input — Years: 20.
  4. 04Substitute these values into the formula: t × (1+a / 100)^(n)
  5. 05Compute Future value: the calculator returns 198.979.
  6. 06Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Savings Bond Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Purchase price ($) halved

P = 50 (from 100)

Keep every other input at its default and halve the purchase price ($). See how future value responds.

  1. 01New Purchase price ($): 50
  2. 02Baseline Future value: 198.979
  3. 03New Future value: 99.4894
  4. 04Future value decreases by 50% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Purchase price ($) doubled

P = 200 (from 100)

Keep every other input at its default and double the purchase price ($). See how future value responds.

  1. 01New Purchase price ($): 200
  2. 02Baseline Future value: 198.979
  3. 03New Future value: 397.958
  4. 04Future value increases by 100% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Annual rate (%) halved

r = 1.75 (from 3.5)

Keep every other input at its default and halve the annual rate (%). See how future value responds.

  1. 01New Annual rate (%): 1.75
  2. 02Baseline Future value: 198.979
  3. 03New Future value: 141.478
  4. 04Future value decreases by 28.9% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Annual rate (%) doubled

r = 7 (from 3.5)

Keep every other input at its default and double the annual rate (%). See how future value responds.

  1. 01New Annual rate (%): 7
  2. 02Baseline Future value: 198.979
  3. 03New Future value: 386.968
  4. 04Future value increases by 94.5% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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