Two pieces of rent arithmetic trip landlords up more than any other: the rent for a part month when a tenancy starts or ends mid-month, and converting a weekly rent to a monthly one. Both have a right method and several wrong ones in common use, and the wrong ones produce disputes and rent rolls that do not reconcile. This page is for the UK landlord working either figure: the daily-rate method for pro rata rent, the correct divisor for rent per week to month, and how the result is entered in the rent roll so the year-end figures are right. The landlord accounts tool on this site holds the rent roll the results go into.
The rent calculator landlords need for a part month: the daily rate method
Take the monthly rent, multiply by twelve to get the annual rent, divide by the number of days in the year to get a daily rate, and multiply by the number of days the tenant occupies in the part month. State in the tenancy agreement that this is the method. Dividing the monthly rent by the days in that particular month gives a different daily rate for February and for March, which is defensible but produces a different answer, and the point is to fix one method and write it down.
Which days count
The day the tenancy starts counts; the day it ends normally counts unless the agreement says otherwise. A tenancy starting on the twentieth of a thirty-day month occupies eleven days of it. Write the start and end dates on the rent roll exactly and let the arithmetic follow them; disputes about pro rata rent are almost always disputes about which days counted.
The divisor a weekly to monthly rent calculator should use
A weekly rent is converted to a monthly one by multiplying by fifty-two and dividing by twelve, because there are fifty-two weeks in a year and twelve months. Multiplying by four undercounts by over four weeks a year; multiplying by four and a third is an approximation of the same figure. A weekly to monthly rent calculator that uses anything but fifty-two over twelve will not reconcile with a year of weekly payments, and the rent roll will show a mysterious surplus or shortfall.
Entering the result in the rent roll
The part-month rent is a rent due line with its own date and amount, followed by the regular monthly rent from the first full month. A converted weekly rent is entered as the monthly figure with the conversion noted, or as weekly due lines if the tenant pays weekly; either way, due and received stay separate so arrears can be read. The rent calculator landlord needs is simply this arithmetic applied consistently, which is what the tools here do.
Why it matters at year end
Rental income for the self-assessment property pages is the rent received in the tax year, and a tenancy that started mid-month or pays weekly is where the received figure and a rough twelve-times-monthly estimate diverge. A rent roll built from correctly calculated due lines and actual receipts gives the year's figure directly; an estimate gives the accountant a question.
Questions people ask about pro rata rent calculator
How do I calculate pro rata rent for a tenancy starting mid-month?
Monthly rent times twelve, divided by the days in the year, times the days occupied in that month. Fix the method in the agreement.
How do I convert rent per week to month?
Weekly rent times fifty-two, divided by twelve. Multiplying by four is wrong by more than four weeks a year.
Should the rent roll hold weekly or monthly figures for a weekly tenant?
Whichever the tenant actually pays, with due and received recorded separately. Convert for comparison, not for the record.