Calculator

Day count conventions

Enter two dates and see the year fraction computed by every supported day count convention, side by side.

Inputs

Period

Start dateD1

End dateD2

Next couponD3 · optional

Frequency

EOM

Comparison

All conventions

Click a row for detail

Convention	ISO	Days	Year fraction
Actual/360	A004	182	0.50555556
Actual/Actual (ICMA)	A006	182	0.50000000
30/360 US (Bond Basis)	A001	180	0.50000000
30E/360 (Eurobond)	A011	180	0.50000000
30E/360 ISDA (German)	A013	180	0.50000000
Actual/365 Fixed	A005	182	0.49863014
Actual/365L	A009	182	0.49726776
Actual/Actual (AFB)	A010	182	0.49726776
Actual/Actual (ISDA)	A008	182	0.49726776

Visualisation

Year fraction comparison

Year fractions range from 0.49726776 (Act/365L, Act/Act AFB and Act/Act ISDA) to 0.50555556 (Act/360) — a spread of 0.00828780. On 10 million nominal at a 5% coupon, that is 4,143.90 of accrued interest.

Reference

Convention guide

Actual/Actual (ICMA)

A006

Actual days divided by actual days in the coupon period, scaled by frequency. Handles irregular periods via notional period generation.

Used for: US Treasury notes and bonds, UK gilts, most European government bonds (including German Bunds), international bonds and Eurobonds

ISDA 2006 §4.16(c), ICMA Rule 251.1(iii)

Actual/Actual (ISDA)

A008

Splits the accrual period at year boundaries. Each portion divided by 365 or 366 depending on whether that year is a leap year.

Used for: Interest rate swaps and other derivatives documented under the ISDA Definitions

ISDA 2006 §4.16(b)

Actual/Actual (AFB)

A010

Actual days with 365 or 366 denominator depending on whether Feb 29 falls in the accrual period. Periods over one year split into whole years plus a stub.

Used for: French government bonds (OATs), some EUR-denominated bonds

FBF 1994, ISDA 1999 paper

Actual/360

A004

Actual days divided by 360. Simple and widely used for money market instruments.

Used for: Money markets, USD and EUR short-term instruments, repos, FRNs

ISDA 2006 §4.16(e)

Actual/365 Fixed

A005

Actual days divided by 365, regardless of leap years.

Used for: GBP money market, some GBP bonds, Australian bonds

ISDA 2006 §4.16(d)

Actual/365L

A009

Actual days divided by 365 or 366. For annual coupons, checks if Feb 29 is in the period. For other frequencies, checks if the end date falls in a leap year.

Used for: Originally designed for Euro-sterling floating rate notes

ICMA Rule 251.1(i) part 2

30/360 US (Bond Basis)

A001

Assumes 30-day months and 360-day years. Applies specific adjustment rules for dates falling on the 31st and end-of-February.

Used for: US corporate bonds, US agency bonds, US municipal bonds

ISDA 2006 §4.16(f)

30E/360 (Eurobond)

A011

European variant of 30/360. Simpler adjustment: any date on the 31st becomes the 30th.

Used for: Eurobonds, EUR-denominated corporate bonds

ISDA 2006 §4.16(g)

30E/360 ISDA (German)

A013

Like 30E/360 but adjusts any last-day-of-month to the 30th, with a special exception for February maturity dates.

Used for: Legacy EUR instruments and swaps that specify it under the ISDA Definitions. Despite the "German" name, current German government bonds (Bunds) use Actual/Actual (ICMA).

ISDA 2006 §4.16(h)

Flat (No accrued interest)

A000

Year fraction is always zero. Used when no accrued interest applies.

Used for: Defaulted bonds, distressed debt, zero-coupon bonds trading flat

ISDA 2006 §4.16(a)