These are the sources we checked each formula against, with the date we read them. Each ratio and calculator page also lists its own sources. We link to sources rather than reproducing them; the explanations on this site are our own. How we choose and use sources is explained on the methodology page.
Operating and Net Margins, NYU Stern School of Business (Aswath Damodaran's faculty data site). Accessed 18 October 2026.
Used for: EBITDA margin.
Variables used in Data Set, NYU Stern School of Business (Aswath Damodaran's faculty data site). Accessed 18 October 2026.
Used for: Operating profit margin, Net operating profit after tax, Return on invested capital, Debt-to-equity ratio (interest-bearing debt only), Enterprise value, EV/EBITDA, EBITDA (from operating income (EBIT)).
Multifamily Selling and Servicing Guide (Part V, Section 416.10C Monitored Debt Service Coverage Ratio, with Glossary; effective September 28, 2026), Fannie Mae. Accessed 18 October 2026.
Used for: Debt service coverage ratio.
Conditions for Use of Non-GAAP Financial Measures, U.S. Securities and Exchange Commission (Federal Register, via GovInfo / U.S. Government Publishing Office). Accessed 18 October 2026.
Used for: EBITDA.
IFRS - IAS 33 Earnings per Share, IFRS Foundation. Accessed 18 October 2026.
Used for: Earnings per share.
Earnings Per Share | Investor.gov, U.S. Securities and Exchange Commission (Investor.gov). Accessed 18 October 2026.
Used for: Earnings per share.
Price-earnings (P/E) Ratio | Investor.gov, U.S. Securities and Exchange Commission (Investor.gov). Accessed 18 October 2026.
Used for: Price-to-earnings ratio.
Comptroller's Handbook: Commercial Real Estate Lending (Version 2.0, March 2022), Office of the Comptroller of the Currency (U.S. Department of the Treasury). Accessed 18 October 2026.
Used for: Debt service coverage ratio.
6.2 Discounts, Markups, and Sales Tax - Contemporary Mathematics | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Markup, Equivalent markup, Selling price for a target markup, Equivalent margin.
9.4 Developing Startup Financial Statements and Projections - Entrepreneurship | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Contribution margin per unit, Break-even point in units.
14.7 Analyzing Financial Statements - Introduction to Business | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Current ratio, Quick ratio (current assets minus inventory), Working capital, Net profit margin, Return on equity, Debt-to-equity ratio.
18.3 Retailing Strategy Decisions - Principles of Marketing | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Gross profit margin, Margin, Markup, Profit per item, Selling price for a target margin, Maximum cost for a target margin, Equivalent markup, Equivalent margin.
6.6 Describe and Prepare Multi-Step and Simple Income Statements for Merchandising Companies - Principles of Accounting, Volume 1: Financial Accounting | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Gross profit margin (from revenue and cost of goods sold), Operating profit margin, Margin.
9.3 Determine the Efficiency of Receivables Management Using Financial Ratios - Principles of Accounting, Volume 1: Financial Accounting | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Receivables turnover, Days sales outstanding.
A Financial Statement Analysis - Principles of Accounting, Volume 1: Financial Accounting | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Current ratio, Quick ratio, Working capital, Net profit margin, Return on assets, Return on equity, Debt-to-equity ratio, Interest coverage ratio, Asset turnover, Inventory turnover, Days inventory outstanding, Receivables turnover.
12.3 Evaluate an Operating Segment or a Project Using Return on Investment, Residual Income, and Economic Value Added - Principles of Accounting, Volume 2: Managerial Accounting | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Return on invested capital.
3.1 Explain Contribution Margin and Calculate Contribution Margin per Unit, Contribution Margin Ratio, and Total Contribution Margin - Principles of Accounting, Volume 2: Managerial Accounting | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Contribution margin per unit, Contribution margin ratio.
3.2 Calculate a Break-Even Point in Units and Dollars - Principles of Accounting, Volume 2: Managerial Accounting | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Break-even point in units, Break-even point in sales.
11.1 Multiple Approaches to Stock Valuation - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Price-to-earnings ratio, Price-to-book ratio, Enterprise value, EV/EBITDA.
19.1 What Is Working Capital? - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Working capital, Inventory turnover, Days inventory outstanding, Days sales outstanding, Days payable outstanding, Cash conversion cycle, Cash conversion cycle (from financial statement figures).
5.1 The Income Statement - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Gross profit margin, Operating profit margin, EBITDA margin, EBIT, EBITDA.
6.2 Operating Efficiency Ratios - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Asset turnover, Inventory turnover, Days inventory outstanding, Receivables turnover.
6.3 Liquidity Ratios - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Current ratio, Quick ratio, Cash ratio.
6.4 Solvency Ratios - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Debt-to-equity ratio, Debt-to-assets ratio, Interest coverage ratio.
6.5 Market Value Ratios - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Earnings per share, Price-to-earnings ratio, Price-to-book ratio.
6.6 Profitability Ratios and the DuPont Method - Principles of Finance | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Net profit margin, Return on assets, Return on equity, Equity multiplier, DuPont analysis, Asset turnover.
6.6 Profitability Ratios and the DuPont Method - Principles of Finance 2e | OpenStax, OpenStax (Rice University). Licence: CC BY-NC-SA 4.0. Accessed 18 October 2026.
Used for: Equity multiplier, DuPont analysis.
acctg211 | Efficiency Ratios, Penn State University (ACCTG 211 course site, oer.hax.psu.edu). Licence: CC BY-SA 4.0. Accessed 18 October 2026.
Used for: Gross profit margin (from revenue and cost of goods sold), Days sales outstanding.
SOP 50 10 8.1 Lender and Development Company Loan Programs with Technical Policy Updates (effective October 1, 2026), U.S. Small Business Administration, Office of Capital Access. Accessed 18 October 2026.
Non-GAAP Financial Measures, U.S. Securities and Exchange Commission, Division of Corporation Finance. Accessed 18 October 2026.
Used for: EBITDA margin, EBITDA, EBITDA (from operating income (EBIT)).