Accrued Interest Calculator
The formula
What the accrued interest tells you
The coupon the seller has earned since the last payment date. Bond quotes are "clean"; the invoice price is "dirty" — clean plus accrued. Misreading the difference is a classic first-trade mistake.
Calculation: AI = face × coupon × days ÷ basis. Enter your inputs and every substitution is shown below the result.
Reading the result
Corporate convention is 30/360 (neat twelve 30-day months); Treasuries use actual/actual; money-market instruments run actual/360. Same coupon, different accrual math.
Rules of thumb: Just a plumbing calculation — always invoice dirty
Limitations and best practice
On default, accrued stops; in distressed trading the clean-price level can be below accrued — a flag that the market is pricing coupon loss.
This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Frequently asked questions
Why do I pay the seller's accrued interest?
Does accrual differ by bond type?
Source & methodology
SIFMA / ICMA standard day-count practice.
How Accrued Interest works — and what your result really means
You are here because you need a specific number, and you want to see how it was produced before you rely on it. Accrued Interest is the kind of number people argue about from memory. This page ends that argument with arithmetic you can watch happen: enter your figures, get Accrued interest in real time, and see every substitution printed below.
In Investing & Markets the same quantity is often quoted under two or three different conventions. The formula printed above fixes one convention and applies it consistently, which is what makes results from this page comparable with each other.
Most confusion about Accrued Interest comes from mixing up the input you control with the input you merely observe. The formula treats them identically, but your decisions should not: one deserves measurement, the other deserves a defensible estimate.
Nothing below is stock text pasted around a number: the worked example computes accrued interest = $10.33 from this tool’s own defaults, and the sensitivity section ranks the inputs that move the result — Face value first, at ≈10.0 % of the headline for a ten-percent error either way in that input. Work down the page and by the end you could re-derive the result in a spreadsheet from memory.
How Accrued Interest is computed, line by line
The engine implements a single stated model: AI = face × coupon × days ÷ basis. There is no hidden coefficient and no login-gated precision — the formula printed is the formula executed, which is also what makes the result citable.
Face value ($) (example value 1,500) is a measured number in the unit named by the label; the formula does not convert for you. This input feeds the formula directly; a defensible figure here is worth more than false precision anywhere else.
Coupon rate (%) (example value 4) is a measured number in the unit named by the label; the formula does not convert for you. Enter it exactly as your document states it — quoted annual, monthly and effective rates are three different numbers.
Days since last coupon (example value 62) is a plain measured quantity — the unit shown in the label is the unit the formula expects. Be precise about the boundary (exact date, start of month); time inputs decide the exponent in most formulas.
Day-count basis (example value 30/360 (corporate & municipal)) is a branching choice rather than a figure you measure; the per-option effects are computed below. If the period is partial, decide whether you mean elapsed or planned time and keep that meaning across every field.
What each “Day-count basis” choice actually does: 30/360 (corporate & municipal) → $10.33 · Actual/365 (Treasuries & agencies) → $10.19 · Actual/360 (money markets) → $10.33 These figures are computed from this engine, not estimated — switch the dropdown above and you will land on exactly these numbers.
Accrued Interest with real numbers, step by step
The tool prints its own working; this is the same arithmetic on the example values, reproduced so you can follow it by hand. Starting figures: Face value ($), Coupon rate (%), Days since last coupon, Day-count basis. The endpoint of that chain is $10.33 of accrued interest, sitting in the “You pay this on top of the quoted price — the clean/dirty split” band.
- AI = $1,500 × 4% × 62 ÷ 360 = $10.33
- The buyer pays the dirty price and receives the next full coupon back on payment day
Per $100 face — 0.689 $. This is the number experienced users quote when the headline alone would mislead.
Annual coupon — $60. Read next to the headline, this is the figure that shows the shape of the trade-off.
Fraction of the coupon period elapsed — 34.4%. This is the number experienced users quote when the headline alone would mislead.
Re-running with your own figures is instant; re-running by hand once is the best way to know the tool is telling you the truth.
Scenario table: Accrued Interest at ±10 % and ±20 % of the key input
Single-point answers invite false confidence, so the same engine was run across a band around the input that matters most here. Each row is a full recalculation of Accrued Interest, not an interpolation.
| Face value setting | Accrued interest |
|---|---|
| 80 % of the example value | $8.27 |
| 90 % of the example value | $9.30 |
| example inputs | $10.33 |
| 110 % of the example value | $11.37 |
| 120 % of the example value | $12.40 |
The corridor runs from $8.27 to $12.40 across that band — which is the range worth planning inside rather than the single $10.33 point estimate. Reproduce it in the form above by editing Face value alone; the substitution steps will follow your figures exactly.
Where Accrued Interest is fragile — and where it is not
This list was computed for this specific engine just now: each numeric input was nudged ±10 % while every other field held its example value, and the accrued interest was recalculated from scratch. For Accrued Interest the ranking is measured rather than guessed, and it belongs to these defaults: shift the starting point and the order can shift with it.
- Nudge Face value by ±10 % and Accrued Interest lands between $9.30 and $11.37 (sensitivity ≈10.0 %)
- Nudge Coupon rate by ±10 % and Accrued Interest lands between $9.30 and $11.37 (sensitivity ≈10.0 %)
- Days since last coupon: ten percent up gives $11.37, ten percent down gives $9.30 — ≈10.0 % of the accrued interest either way
Face value is the dominant lever here: ten percent either way moves the result by about 10.0 %, from $9.30 to $11.37. Spend your verification effort there first, and Coupon rate is effectively tied with it (≈10.0 % for the same nudge), so verify the pair together. Everything below that can stay approximate, which is a licence to stop chasing data that would not change the decision.
What an Accrued Interest of $10.33 means in practice
The value above only becomes useful the moment you know what it is being measured against. On the example inputs the band reads “You pay this on top of the quoted price — the clean/dirty split”; your own figures place you on a different rung of the same ladder. Before treating the band as fact, note its width: ten percent either way on Face value already spans $9.30 to $11.37. The practical reading rules: ask what would have to change to move you one band. If the answer is “a small, plausible input difference”, the band itself is not the finding — the uncertainty is.
Compared with charting sites, this page explains the formula rather than hiding it — the goal is a number you can defend in a meeting, not just display.
Common mistakes with Accrued Interest (and the fix)
On default, accrued stops; in distressed trading the clean-price level can be below accrued — a flag that the market is pricing coupon loss. This calculator gives an estimate based on standard formulas; it is not professional financial, medical, legal or engineering advice. Verify anything you plan to act on with a qualified professional and your own records.
Using stale inputs. Accrued Interest is only as current as the numbers behind it — an estimate carried over from a previous season, rate table or report quietly biases every output. Re-measure the inputs first; that single habit fixes more bad Accrued Interest figures than any formula change.
This model has its own particular trap: Face value carries ≈10.0 % of the response per ten percent of error, so effort spent elsewhere is largely decorative.
A final trap is presentation: reporting Accrued Interest to more decimal places than the inputs support. The tool prints what the arithmetic gives; you should quote only what your least precise field justifies.
Accrued Interest verification checklist
- Compare the output against one published benchmark or a colleague’s independent estimate.
- Confirm the example values are plausible for your own situation before replacing them.
- Check Face value before anything else: it is the measured dominant input, ≈10.0 % of Accrued Interest per ten percent.
- Note the date and the inputs beside the number so the figure can be audited later.
- Recompute once with the dominant input deliberately set low, and see whether the decision changes.
- Run the ±10 % stress on the top two levers and check that your conclusion survives both.
A routine for decision-grade Accrued Interest
Using a calculator well sounds trivial, but the difference between a decision-grade figure and a throwaway one lives entirely in the routine. The routine for Accrued Interest takes a minute to learn and applies to every input above.
Step 1 — collect, then type. Everything this tool asks for is listed above (face value ($), coupon rate (%), days since last coupon, day-count basis). Pull each figure from something you can point at — paperwork, a dashboard, a label — before touching a field. Guesswork at the input stage cannot be repaired at the interpretation stage. When two sources disagree, it is almost never the arithmetic that differs.
Step 2 — compute the version you would not be embarrassed by. If a stranger audited your inputs, which set would you hand over? Enter that set, read the result, and treat everything else as upside. Most surprises in numbers are surprises about inputs, not about formulas.
Step 3 — isolate your variables. Change one field, observe, revert. The live sensitivity list does the ranking for the default inputs; verify it against your own, because dominance shifts when the starting point shifts. Most surprises in numbers are surprises about inputs, not about formulas.
Step 4 — run the scenario trio. Expected, pessimistic, optimistic. The gap between pessimistic and expected is the number to plan against; the optimistic result is useful only as a ceiling. A figure with a date beside it becomes evidence; without one it stays an anecdote.
Step 5 — save the story with the figure. A number without its inputs and its date is unusable within a quarter. Record $10.33, the assumptions behind it, and today’s date; your future self will be auditing a stranger’s arithmetic. Comparisons are cheap: run the identical calculation for the alternative and look at the gap.
From calculation to decision: where Accrued Interest earns its keep
Investing & Markets arguments end at arithmetic or they do not end. Accrued Interest is the arithmetic: $10.33 on the example inputs, reproducible by anyone who types the same numbers. When in doubt, prefer the boring input: the interesting one is usually the one you misread.
The companion outputs — Per $100 face and Annual coupon — exist for the second stage of that screen: the headline sizes the prize, while the companions describe the trade-off you are accepting to get it. Comparisons are cheap: run the identical calculation for the alternative and look at the gap.
Nothing here is stored or transmitted, so the habit of checking is free: open the page, re-enter current figures, compare with the number you saved last time. Half of a good calculation is knowing which input you would hate to be wrong about.
Accrued Interest — frequently asked questions
What affects Accrued Interest the most?
The short answer: Face value. The longer answer is the sensitivity table on this page, where every numeric input was probed by ten percent and the accrued interest recalculated — Face value moved it furthest, by roughly 10.0 % ($9.30 to $11.37).
Do coupon rate and face value matter equally?
Accrued Interest here is co-driven: Face value and Coupon rate produced ≈10.0 % and ≈10.0 % responses, which is a tie for practical purposes. Everything below those two is a rounding error by comparison.
How much does the “Day-count basis” choice change the answer?
The spread is not cosmetic: this choice alone takes Accrued Interest from $10.19 to $10.33 with every other input frozen, which is more influence than most of the numeric fields on this page can claim.
What is a typical Accrued Interest?
With the example inputs on this page the result is $10.33, labelled “You pay this on top of the quoted price — the clean/dirty split”. “Typical” varies with situation, which is why every result here ships with its verdict band and its sensitivity list: they turn one figure into a range you can locate yourself inside.
How do I calculate Accrued Interest by hand?
AI = face × coupon × days ÷ basis is the entire method. Work the inputs in that order — AI = $1,500 × 4% × 62 ÷ 360 = $10.33 — and you will reach $10.33 on the default figures, the same number this tool prints.
What happens to Accrued Interest if face value changes by 10 %?
Try it in the form above and the printed substitution will follow you; the pre-computed answer for the defaults is $9.30 to $11.37 across the ten-percent probe, i.e. ≈10.0 % sensitivity on the accrued interest.
Is the Accrued Interest result of $10.33 good or bad?
Neither, on its own — the label “You pay this on top of the quoted price — the clean/dirty split” is the band this figure falls in for the example inputs, and your own inputs will place you elsewhere on the same ladder. Judge the number against your history and your alternatives, and remember that a ten-percent error in Face value alone moves it by ≈10.0 %.
How do I calculate Accrued Interest manually?
Write down the inputs, then follow the printed steps in order — AI = face × coupon × days ÷ basis. A spreadsheet replicates it with two or three cells. The manual route is worth doing once to build intuition; after that the calculator saves time and eliminates transcription slips.
Can I predict future returns with Accrued Interest?
No tool predicts; Accrued Interest computes implications. Use it to ask "if these inputs hold, what follows" — then stress the assumptions.
Why do I pay the seller's accrued interest?
Because you will collect the entire next coupon, including the days the seller held the bond. The accrual transfer keeps the coupon split fair.
Does accrual differ by bond type?
Yes — corporates and munis mostly use 30/360 (each month counts as 30 days), Treasuries actual/actual, and money-market instruments actual/360. Same coupon, different arithmetic.
Do I need an account to use this Accrued Interest calculator?
No, and no data leaves the tab. The engine runs in the page itself, which is why the worked example, the bands and the sensitivity ranking all respond instantly to your keystrokes.
What the labels on this page mean
- Per $100 face
- 0.689 $ on the example inputs — a companion figure printed beside the headline of Accrued Interest so that no result is read in isolation.
- Annual coupon
- $60 on the example inputs — a companion figure printed beside the headline of Accrued Interest so that no result is read in isolation.
- Fraction of the coupon period elapsed
- 34.4% for the Accrued Interest worked case; it sits next to the main result because it carries context the headline leaves out.
- Accrued interest
- The primary output of this tool: $10.33 for the default inputs, computed exactly from AI = face × coupon × days ÷ basis.
- Worked example
- The step-by-step substitution printed above, so the arithmetic can be re-derived by hand or in a spreadsheet.
- Verdict band
- The plain-language label — here “You pay this on top of the quoted price — the clean/dirty split” — mapping the computed figure onto experience-based ranges for Investing & Markets.
- Sensitivity (±10 %)
- How far the Accrued Interest moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.
Where the Accrued Interest model comes from
There is no black box on this page — the engine evaluates AI = face × coupon × days ÷ basis. Source of record: SIFMA / ICMA standard day-count practice. Any other implementation of this model should return the same figure for the same inputs. If one does not, the difference is in its assumptions — which this page prints and that one probably does not.
Treat the output as a precise answer to the question you typed: exact arithmetic, transparent formula, published source, no hidden rounding. Nothing is smoothed, weighted or adjusted behind the scenes; where judgement enters, this page says so and names the input responsible.
After the number: what to do with it
Re-run the calculation with your own figures, stress the two most sensitive inputs by ±10 %, and only then act on the result.
Whoever you are (people who need one trustworthy number before their next decision), the next step is the same: replace the example inputs with your own, note the date, and re-run whenever a figure moves. In Investing & Markets, a dated figure is a trend, and an undated one is a rumour.