Our Methodology

This page exists because a calculator is only as trustworthy as the formula and sources behind it. It explains, in plain terms, how we build each tool on OtherCalculators, where the numbers in our formulas come from, how often we review a page after publishing it, and — just as important — what our tools are not qualified to tell you. If anything below doesn't match what you see on a specific calculator, treat that as a bug and let us know using the link at the bottom of this page.

How we build our calculators

Every calculator on OtherCalculators runs a published, checkable formula — never a black box. Our team writes the calculation directly into the tool's code: the same arithmetic you could work through by hand with a formula sheet and a calculator. Every input field on the page maps to a real variable in that formula, and every default value is visible and editable — nothing is estimated behind the scenes that isn't shown on the page itself. For example, our asphalt tonnage calculator defaults to roughly 145 lb per cubic foot for compacted asphalt, a standard industry figure you can see, and override, directly in the tool.

Where our formulas come from

We do not invent the numbers our formulas depend on. Where a governing or standards body publishes the rule, we follow it:

• 401(k) contribution and loan calculators follow rules published by the IRS — see the IRS's 401(k) plans overview and Retirement topics – Plan loans.
• Asphalt density, thickness, and coverage conventions follow general paving-industry engineering practice, informed by organizations such as the Asphalt Institute and ASTM International, alongside individual state Department of Transportation (DOT) paving specifications. State DOT specs vary by state, so we describe them in the tool's help text rather than linking a single source that would only be correct for one state.
• AP score calculators follow the 1–5 scoring scale published by the College Board.

Where no single authoritative source exists — for example, a rule-of-thumb waste-factor percentage on a paving estimate — we say so directly in the calculator's help text instead of attaching a citation that doesn't exist.

How we handle cost estimates

Every cost-related calculator on this site — driveway cost, paving cost, resurfacing cost, and similar tools — produces a range, not a quote. Material and labor prices vary by region, supplier, season, and job complexity, and we have no live pricing feed behind these tools. The dollar figures they return are built from typical unit-cost ranges, meant to help you budget and compare options, not to replace a quote from a contractor or supplier. Treat any cost output as a starting point for a conversation, not a number to hold a vendor to.

Review and update cycle

Every page on OtherCalculators carries a visible “Last updated” date, drawn from the same record that generates the page's structured data — the two are never allowed to disagree. We revisit a calculator when a user reports an error through /contact, when a source figure changes (a state paving spec update, or an IRS limit changing for the year), or when we materially rewrite a page's content. A page's “Last updated” date reflects the most recent one of those events — a page that hasn't changed keeps its original date rather than being stamped with today's date for appearance's sake.

Accuracy, limitations, and what our tools are NOT

Our calculators are estimation tools, not professional advice.

• Financial calculators (401(k), loans, savings) are not financial, tax, or legal advice, and are not a substitute for a licensed financial advisor, CPA, or attorney. Contribution limits, loan rules, and tax treatment can change, and your specific plan may differ from what a general calculator assumes.
• Asphalt and paving calculators are planning estimates. Actual material needs depend on site conditions, compaction, sub-base, and supplier-specific density, and should be confirmed with your paving contractor or supplier before ordering material.
• AP score calculators reflect publicly published scoring conventions, not a guarantee of any individual's actual exam outcome.

We do not employ a licensed engineer, CPA, or financial advisor to review these tools, and we make no claim otherwise. If a calculator's output materially affects a financial or construction decision, verify it against a professional or the primary source before acting on it.