Calculation Methodology

Every dollar figure on TheFinSense is computed, not estimated. This page documents the formulas, the verification process, and the reproducibility standard behind our numbers. It is the technical companion to our Editorial Policy, which covers authorship, sourcing, and corrections.

The Core Formula

Long-horizon projections use the monthly-compounded future value of a lump sum plus a recurring contribution. For an initial amount P, a monthly contribution C, an annual rate r, and a horizon of t years:

The same monthly periodicity is applied to every rate input so that lump-sum growth and contribution growth are compounded on identical terms. Where an article uses a different model (for example a real-rate or fee-drag adjustment), that variation is stated in the article’s own methodology box.

Our Verification Standard

No figure is published on the strength of a spreadsheet alone. Each one passes a fixed set of checks:

• Python-verified: every future value is recomputed in Python and must match the published figure within a $10 tolerance before it ships.
• Sensitivity-tested: each projection is run across a minimum of five variable scenarios (rate, horizon, contribution, or starting balance) so the conclusion is shown to hold, not asserted.
• Source-dated: every rate input (federal funds rate, HYSA yields, expense ratios, contribution limits) carries its source URL and the date it was retrieved.
• Parameter-disclosed: all case-study inputs appear in a visible table inside the article. Nothing material is hidden in the prose.

Reproducibility

Where an article’s conclusion rests on a non-trivial calculation or a backtest, we publish the underlying notebook so any reader can rerun it and check the arithmetic line by line. The notebook reproduces the exact figures printed in the article from the same inputs. We treat this first-hand, reproducible work as the core of our analysis, not a footnote to it.

When a notebook is published for an article, it is linked directly from that article’s methodology box.

What Counts as a Source

Calculations are built only on primary evidence. We do not derive figures from aggregator sites or secondary summaries. In order of preference:

• Official rate and limit data (Federal Reserve / FRED, IRS Revenue Procedures, SEC EDGAR filings)
• Peer-reviewed journal papers, NBER working papers, and SSRN preprints
• Named institutional research (Vanguard, EBRI, Morningstar, DALBAR)
• Official platform documentation (broker fee schedules, account disclosures)

Where a figure from secondary research is contested, we present it alongside its counterpoint rather than as settled fact.

The Per-Article Methodology Box

This page covers the standards common to every article. Each article also carries its own methodology box with the specifics for that piece: the exact inputs used, any model variation, the data retrieval dates, and a link to the reproducible notebook where one exists. The box links back to this page so the general standard and the article-specific detail are always one click apart.

Corrections to Calculations

If a calculation error is identified after publication, the article is corrected immediately and a visible correction note records the original and corrected values. Our full review and correction cycle is described in the Editorial Policy.

Contact

Questions about a specific calculation, our formulas, or a reproducible notebook can be directed to our Contact page.