Day Count Actual360 calculator
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Formula
The Actual/360 convention divides the annual interest rate by 360 to obtain the daily rate, then multiplies by the actual number of calendar days in the period. This produces a year fraction of Actual Days / 360, which is used as the accrual factor for interest calculations.
Last reviewed: December 2025
Worked Examples
Example 1: Commercial Loan Interest (6 Months)
Example 2: Bond Accrued Interest Comparison
Background & Theory
The Day Count Actual360 Calculator applies the following established principles and formulas. Legal and compliance calculations form the quantitative backbone of risk management across every industry. Statute of limitations periods define the window within which legal action must be initiated; missing these deadlines extinguishes claims permanently regardless of their merit. Periods vary widely by jurisdiction and claim type: contract disputes typically allow 3-6 years, personal injury claims 2-3 years, and written contracts may allow up to 10 years in some states. Calculating expiry dates requires identifying the triggering event, applying the statutory period, and accounting for tolling provisions that pause the clock during minority, incapacity, or fraudulent concealment. Employment law generates substantial calculation requirements. The Fair Labor Standards Act mandates overtime pay at 1.5 times the regular rate for hours worked beyond 40 in a workweek. Regular rate calculation is not simply the hourly wage; it must incorporate non-discretionary bonuses, shift differentials, and commissions, divided by total hours worked. Workers' compensation premiums are computed as payroll divided by 100, multiplied by the applicable class code rate, adjusted by an experience modification factor reflecting the employer's historical claims. GDPR and similar data privacy regulations impose specific retention and deletion timelines. Personal data may not be kept longer than necessary for its original purpose, requiring organisations to maintain deletion schedules and document the legal basis for each data category. Regulatory filing deadlines in financial services, environmental compliance, and healthcare are typically expressed in business days, necessitating accurate weekday and holiday calendars. Legal cost-benefit analysis quantifies litigation risk by multiplying potential damages by probability of adverse judgment, comparing expected loss against settlement or compliance investment. Liability insurance premiums reflect actuarial assessments of this expected loss, modified by coverage limits, deductibles, and risk management practices. Compliance programmes that demonstrably reduce violation probability directly reduce premium costs and regulatory exposure.
History
The history behind the Day Count Actual360 Calculator traces back through the following developments. The formalisation of legal obligations through written codes began with the Code of Hammurabi around 1754 BCE in ancient Babylon. Carved onto a basalt stele, it established 282 laws governing commerce, property, and personal conduct, notably applying proportional penalties based on social status. The principle that legal consequences follow determinable formulas rather than arbitrary judgment traces directly to this tradition. Roman law provided the systematic framework that shaped Western legal systems. The Twelve Tables (450 BCE) codified customary law for public access, and the Corpus Juris Civilis compiled by Emperor Justinian in 529-534 CE synthesised centuries of legal development into an authoritative reference that influenced European jurisprudence for a millennium. Magna Carta in 1215 established the revolutionary principle that even monarchs were subject to law, laying the groundwork for due process, proportional punishment, and the right to a fair hearing. English common law evolved through judicial decisions rather than codification, creating a precedent-based system that spread through British colonisation to become the legal foundation of the United States, Canada, Australia, and India. The Napoleonic Code of 1804 revived the Roman codification tradition, systematising French civil law and inspiring legal reforms across continental Europe, Latin America, and parts of Africa. Its clear structure influenced how modern compliance regulations are drafted. The New Deal era of the 1930s dramatically expanded the American regulatory state, creating agencies like the SEC, NLRB, and FDA with broad rulemaking authority. This expansion made compliance a distinct professional discipline. The Sarbanes-Oxley Act of 2002, passed in response to Enron and WorldCom scandals, institutionalised compliance functions within public companies by mandating internal controls, audit committees, and executive certification of financial statements. GDPR's implementation in 2018 similarly professionalised data protection compliance globally, creating an entirely new category of compliance calculation centred on data lifecycle management.
Frequently Asked Questions
Formula
Interest = Principal × (Annual Rate / 360) × Actual Days
The Actual/360 convention divides the annual interest rate by 360 to obtain the daily rate, then multiplies by the actual number of calendar days in the period. This produces a year fraction of Actual Days / 360, which is used as the accrual factor for interest calculations.
Worked Examples
Example 1: Commercial Loan Interest (6 Months)
Problem: Calculate interest on a $250,000 loan at 6.25% from March 1 to September 1 using Actual/360.
Solution: Actual days: March(31) + Apr(30) + May(31) + Jun(30) + Jul(31) + Aug(31) = 184 days\nYear fraction (Actual/360): 184 / 360 = 0.51111\nInterest = $250,000 × 6.25% × 0.51111 = $7,986.11
Result: Interest (Actual/360) = $7,986.11
Example 2: Bond Accrued Interest Comparison
Problem: Compare accrued interest on a $1,000,000 bond at 4.5% from Jan 15 to Jul 15 using Actual/360 vs Actual/365.
Solution: Actual days: Jan(16) + Feb(29) + Mar(31) + Apr(30) + May(31) + Jun(30) + Jul(15) = 182 days\nActual/360: $1,000,000 × 4.5% × 182/360 = $22,750.00\nActual/365: $1,000,000 × 4.5% × 182/365 = $22,438.36\nDifference: $311.64 more under Actual/360
Result: Actual/360: $22,750 | Actual/365: $22,438.36 | Diff: $311.64
Frequently Asked Questions
What is the Actual/360 day count convention?
The Actual/360 day count convention calculates interest by dividing the actual number of days in a period by 360 days per year. This method is widely used for money market instruments, commercial loans, and LIBOR/SOFR-based floating rate products. Because it divides by 360 instead of the actual 365 or 366 days in a year, it effectively charges slightly more interest than an Actual/365 convention for the same annual rate. For every full calendar year, the borrower pays interest for 365/360 = 1.01389 year fractions, resulting in approximately 1.4% more interest than Actual/365. This makes Actual/360 more favorable to lenders.
What is the difference between Actual/360 and 30/360 day count conventions?
Actual/360 uses the real calendar number of days between two dates divided by 360, while 30/360 assumes every month has exactly 30 days and divides by 360. For example, from January 15 to February 15 is 31 actual days under Actual/360 but exactly 30 days under 30/360. The 30/360 convention (also called Bond Basis) is simpler to calculate and is commonly used for corporate and municipal bonds, while Actual/360 is standard for money markets, LIBOR-based loans, and many floating-rate instruments. The choice of convention can significantly impact interest amounts, especially over longer periods or with large principal amounts.
Why do banks use Actual/360 instead of Actual/365?
Banks prefer Actual/360 for commercial lending because it generates slightly higher interest income. When the annual rate is divided by 360 instead of 365, the daily rate is higher (e.g., 5% / 360 = 0.01389% vs. 5% / 365 = 0.01370% per day). Over a full 365-day year, this results in approximately 1.39% more interest collected. For a $1,000,000 loan at 5%, the difference is about $694 per year. This convention also aligns with the historical banking practice of using a 360-day year for simplified calculations. Regulators and courts have upheld this practice as standard, though borrowers should be aware of its effect on effective interest rates.
How does the Actual/360 convention affect mortgage calculations?
While residential mortgages typically use the Actual/365 or 30/360 convention, some commercial mortgages and adjustable-rate mortgages use Actual/360. This means the borrower pays interest on 365 days but the daily rate is calculated using a 360-day year, resulting in higher effective interest. For a $500,000 commercial mortgage at 6%, the annual interest using Actual/360 is approximately $30,416.67 (365 × $500,000 × 6% / 360) versus $30,000 using Actual/365, a difference of $416.67 per year. Over a 10-year loan term, this can add up to several thousand dollars in additional interest, making it important to verify which convention is specified in loan documents.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
Can I use the results for professional or academic purposes?
You may use the results for reference and educational purposes. For professional reports, academic papers, or critical decisions, we recommend verifying outputs against peer-reviewed sources or consulting a qualified expert in the relevant field.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy