Fidamen

Personal Loan Payment Interest-Only Estimator

This estimator calculates the interest-only payment for a personal loan given the loan principal, annual interest rate (APR), number of payments per year, and the length of the interest-only period. It shows the periodic payment, annual interest cost, and total interest paid during the interest-only period.

Use this tool to compare quick estimates before requesting firm loan terms from a lender. This tool provides indicative values only and does not replace loan disclosures, underwriting, or legally required pricing documents.

Updated Nov 3, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 6cb91d70b24d • Reviewed by Fidamen Standards Committee

Inputs

Results

Updates as you type

Periodic interest-only payment

$58.33

Annual interest-only payment

$700.00

Total interest paid during interest-only period

$700.00

Interest rate per payment period

0.58%

OutputValueUnit
Periodic interest-only payment$58.33USD
Annual interest-only payment$700.00USD
Total interest paid during interest-only period$700.00USD
Interest rate per payment period0.58%%
Primary result$58.33

Visualization

Methodology

The calculator applies straightforward interest-only math: interest accrues on the outstanding principal and only interest is paid during the interest-only period. No principal is amortized in that phase.

For transparency and traceability, the calculation and numeric behavior are designed with software quality and numerical precision guidance in mind. Refer to NIST guidance for secure and auditable computation practices, ISO standards for software lifecycle and quality control, and IEEE best practices for numerical computing and rounding behavior.

Accuracy caveat: results are rounded for display and assume interest is computed on a simple nominal APR basis with the specified payment frequency. Actual lender calculations can use different day count conventions, compounding rules, or fees which alter payments and totals. Always confirm with the lender's loan agreement.

Worked examples

Example 1: $10,000 principal, 6% APR, 12 payments/year, 1-year IO period → periodic = $50.00, annual = $600.00, total IO = $600.00.

Example 2: $25,000 principal, 8% APR, 12 payments/year, 2-year IO period → periodic = $166.67, annual = $2,000.00, total IO = $4,000.00.

F.A.Q.

Is the interest-only payment the same as the minimum payment a lender may require?

Not necessarily. This calculator shows the pure interest amount based on the inputs. Lenders may require additional fees, escrow, or minimum principal repayments that increase the periodic payment.

Does this calculator show what happens after the interest-only period ends?

No. This estimator only computes interest-only payments and totals for the interest-only phase. To model post-interest-only amortization, run a separate amortizing payment calculation using the remaining term and any principal balance.

How accurate are the numbers?

Displayed values are accurate to common monetary rounding rules but do not include lender fees, different compounding conventions, or day-count rules. For contractual terms, rely on lender disclosures and underwriting. This tool follows software quality guidance but is not a substitute for regulated loan documents.

Sources & citations

Further resources

Versioning & Change Control

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

Record ID: 6cb91d70b24d

What changed (latest)

v1.0.0 • 2025-11-03 • 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 3, 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 • 2025-11-03 • 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: 53ff12199db0