What is the equivalent ACT/365 interest rate for a loan quoted at 8.00% on ACT/360?

Multiply the ACT/360 rate by (365 ÷ 360): 8.00% × (365 ÷ 360) = 8.1111% per annum on a 365-day year (an extra 11.11 basis points per year).

What happens in a 366-day leap year under Actual/365 (Fixed)?

Under Actual/365 (Fixed), the denominator remains fixed at 365 even during a leap year. If a loan runs for all 366 days of a leap year, the day-count fraction is 366 ÷ 365 = 1.00274.

Why do corporate bonds use 30/360 instead of Actual/365?

Under 30/360, every calendar month has 30 days and every 6-month coupon period has 180 days (180 ÷ 360 = 0.50). That guarantees a semi-annual bond pays the exact same rupee coupon every 6 months regardless of whether the half-year contains 181, 182, or 184 calendar days.

How does Actual/Actual (ISDA) handle a loan that starts in 2027 and ends in leap year 2028?

ISDA splits the accrual period at midnight on December 31: days falling in non-leap year 2027 are divided by 365, and days falling in leap year 2028 are divided by 366.

Compare ACT/365, ACT/360 & 30/360 Day-Count Interest

The four standard day-count conventions: ACT/365F, ACT/360, ACT/ACT (ISDA), and 30/360

Every file format and statutory compliance rule has a deterministic structure underneath the user interface. When teams rely on manual spreadsheet edits or generic cloud converters, subtle structural details get lost: page coordinate boxes reset, check digits go unverified, or rounding rules drift by several hundred rupees across a financial year. Understanding the exact specification behind Day-Count Interest lets you verify every output before it enters an audit file or government portal.

The reference table below summarizes the core technical and statutory parameters enforced by the local engine:

Parameter / Rule	Specification / Formula	Practical Audit Impact
Actual / 365 (Fixed)	`DCF = Actual Calendar Days ÷ 365 (even in a 366-day leap year)`	Standard for Indian Rupee (INR) bank loans, CC/OD limits, and FDs
Actual / 360 (Money Market)	`DCF = Actual Calendar Days ÷ 360`	Standard for USD/EUR money market & ECB lines; yields 365/360 = 1.01389× over a full year
Actual / Actual (ISDA)	`DCF = (Days in Non-Leap Yr ÷ 365) + (Days in Leap Yr ÷ 366)`	Splits accrual periods that straddle a leap-year boundary (Dec 31 / Jan 1)
30 / 360 (Bond Basis)	`ΔD = 360(Y₂−Y₁) + 30(M₂−M₁) + (D₂−D₁) with D=31 → 30 rules`	Each month treated as 30 days so every semi-annual coupon equals exactly 180/360 = 0.50

Because each rule above is evaluated directly in your browser tab using typed JavaScript arrays and WebAssembly workers, there is no server queue, no file-count cap, and zero external data retention. Every byte of the source document or ledger table is parsed inside volatile browser memory and released as soon as the tab closes.

How day-count numerators (exclude start date, include end date) are counted

Running this workflow in Day-Count Convention Interest Calculator takes four deterministic steps from raw input to verified output:

Open Day-Count Convention Interest Calculator and enter the Principal Amount, Annual Nominal Rate (%), Accrual Start Date, and Accrual End Date.
Inspect the side-by-side comparison table showing the Day Numerator, Year Denominator, Day-Count Fraction, and Accrued Interest across ACT/365 Fixed, ACT/360, ACT/ACT (ISDA), and 30/360.
Check the Rupee variance column to verify your bank interest debit note or bond coupon calculation.
Export the accrual audit breakdown as CSV for treasury sign-off.

Note: All inputs, uploaded files, and intermediate calculations remain in volatile browser RAM. Closing or refreshing the tab clears the memory buffer immediately.

When you process recurring monthly batches, keeping the input schema consistent across runs ensures that downstream checks in related guides such as calculate msme 45 day late payment compound interest, run 3 step and 5 step dupont roe analysis, calculate tds under section 194c 194j 194h 194i match to the exact rupee or byte. Before starting a large batch, verify that your source file is not locked by an unknown password and that column headers or page indices match the expected range.

Step-by-step: auditing loan and bond interest accruals in ShiftTools

Auditing a ₹10,00,00,000 Credit Line at 9.00% p.a. from Jan 15, 2026 to Jul 14, 2026

A treasury manager audits an interest debit for a ₹10,00,00,000 (₹10 Cr) tranche drawn on January 15, 2026 and repaid on July 14, 2026 at 9.00% p.a. Counting actual calendar days (excluding Jan 15, including Jul 14): Jan (16) + Feb (28) + Mar (31) + Apr (30) + May (31) + Jun (30) + Jul (14) = 180 actual days. Under 30/360: 360(0) + 30(7−1) + (14−15) = 180 − 1 = 179 days. Comparing the accrued interest across conventions: ACT/365 (Fixed) = ₹10 Cr × 0.09 × (180 ÷ 365) = ₹44,38,356.16; ACT/360 = ₹10 Cr × 0.09 × (180 ÷ 360) = ₹45,00,000.00 (+₹61,643.84 vs ACT/365); 30/360 = ₹10 Cr × 0.09 × (179 ÷ 360) = ₹44,75,000.00.

TEXT

Principal: ₹10,00,00,000 | Nominal Rate: 9.00% p.a. | Period: 2026-01-15 to 2026-07-14
---------------------------------------------------------------------------------------
Convention            Numerator   Denominator   Day Fraction    Accrued Interest (₹)
1. ACT / 365 (Fixed)   180 days      365         0.49315068        ₹44,38,356.16
2. ACT / ACT (ISDA)    180 days      365         0.49315068        ₹44,38,356.16
3. 30 / 360 (Bond)     179 days      360         0.49722222        ₹44,75,000.00
4. ACT / 360 (MMkt)    180 days      360         0.50000000        ₹45,00,000.00

You can reproduce this exact calculation at any time by pasting the sample values above into Day-Count Interest and comparing the generated summary row against your internal workpaper. Recording the input parameters alongside the output file creates a self-contained audit trail for statutory or peer review.

Worked example: ₹10 Crore facility from Jan 15 to Jul 14 across all 4 conventions

In production accounting and document engineering workflows, edge cases appear when inputs combine multiple conventions in a single batch. For example, a merged PDF bundle may mix portrait A4 text pages (/MediaBox 595.28 × 841.89 pt) with wide environment annexures, or a quarterly ledger export may combine April-to-September transactions with October-to-March entries after a mid-year threshold revision.

To prevent silent errors across those boundaries, always inspect the per-item diagnostic status before exporting the final file:

Verify unit consistency: Confirm whether input figures represent monthly vs annual amounts, GST-exclusive vs GST-inclusive values, or 1-based physical page indices vs printed document numbers.
Check boundary conditions: Pay close attention to exact threshold cutoffs, leap-year day counts, and page rotation multiples (0, 90, 180, 270 degrees) where off-by-one errors commonly occur in manual spreadsheets.
Preserve audit trails: Save the exported summary CSV or processed PDF alongside the raw source file so any reviewer can trace the transformation step by step without re-keying data.
Cross-check neighbour utilities: Pair Day-Count Interest with companion tools in the Accounting & Finance suite (calculate msme 45 day late payment compound interest, run 3 step and 5 step dupont roe analysis, calculate tds under section 194c 194j 194h 194i) when a task spans multiple stages.

Leap-year effects (366 days) and month-end 30/360 adjustment rules

Standard banking accrual counts either the first day or the last day of an interest period, never both ("include start date, exclude maturity date" = D₂ − D₁ days). Only when checking inclusive trade-date spans (such as Indian CC/OD daily product sheets where both opening and closing dates carry end-of-day utilization) do you add +1 day to the numerator.

Limit: Client-side browser execution verifies mathematical formulas, statutory rules, and binary file structures offline. Where a regulation requires live portal authentication (such as checking active GST registration status on the GSTN portal or verifying operative PAN-Aadhaar linkage on TRACES), perform that portal check alongside your local calculation.

By separating deterministic local computation from external portal lookups, your team eliminates manual formatting and calculation errors while keeping sensitive client files off third-party cloud servers.