A “paydown factor” basically tells us how much of the principal amount of borrowed money is paid back in a given month.
As an example, let’s look at Vlad. (No, really, everyone look at Vlad.) Vlad is a homeowner with a $2,000 monthly mortgage payment. His original mortgage loan was for $350,000, and he’s locked in at a 3.5% interest rate. According to his statement, $1,300 of last month’s mortgage payment went toward the principal, while the other $700 went to interest. If we want to calculate the paydown factor, all we have to do is divide $1,300 by $350,000. When we do, we get .0037, which tells us that Vlad paid off .37% of his loan principal last month.
Vlad’s a multifaceted kind of guy, so in addition to owning a home, he also invests in mortgage-backed securities, or MBSs. We bring this up because paydown factors have uses outside of individual mortgage calculations. For example, calculating the paydown factor for MBSs works just like it does for single mortgages: we just look at how much of the overall principal amount was paid back in a given month, divide it by the overall principal amount, and voila. MBS paydown factor.
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Finance Allah shmoop What are the components of a mortgage
payment All right so here's a weird thing about mortgages
When you borrow say four hundred grand buy a home
and say in a six percent fixed thirty year interest
you'll end up paying way more than the four hundred
grand just in interest Renting the money Think about it
Well you'll have a monthly pay payment of twenty four
hundred bucks and by the time you've made thirty times
twelve per year or three hundred sixty payments you'll have
paid some four hundred sixty three thousand dollars in interest
charges Seems like a lot of money to pay out
of your own pocket But since mortgage interest is usually
entirely tax deductible well the rial cost to most home
borrowers is actually meaningful E less than that six percent
interest maybe something closer to a three and a half
four percent something like that So while yes on a
total gross basis you will have paid out more than
the amount borrowed over the thirty year course in the
mortgage you'll also have been forgiven loads of taxes And
for what it's worth over most thirty year time periods
in history the market has gone up about eight to
ten percent a year on average Compound did something like
that So you feel the people mover floor moving fast
underfoot with inflation pushing things around as you go along
Well the money you borrow is the principal of the
loan and that number usually declines by a small amount
each month As you make a flat payment and it's
usually gradually paid off Check out what the principal of
four hundred grand looks like for the first twelve months
of payments right here Note that the flat monthly payment
is twenty four hundred dollars and see how the principal
payed as part of this payment loan thing there goes
from paydown of three hundred ninety eight dollars Teo Well
four hundred twenty a year later right Like you're paying
off principal little by little So you have less that's
attributed to interest And Mohr that's attributed to principal pay
down as you go along and note that this assumes
Ah flat monthly payment here Right You're paying the same
amount You're one you would You're thirty two thousand three
hundred ninety eight dollars and twenty cents on this particular
alone So after a year the amount owed an interest
is well just slightly last Here in this example it's
one thousand nine hundred seventy seven bucks down from in
a two grand and note what it looks like at
the end of each of the first five years That's
a big shift from almost entirely interest do now Principal
being ah meaningful part of it you got after ten
years right here and then at the halfway point in
fifteen years it's here So I noticed that the amount
owed at this point is roughly half the total Why
Because the lion share the pay down went to interest
in the first half of the life of the mortgage
AII those first fifteen years and well then in the
back half way more will be attributed to a principal
pay down than to interest Like check out what the
very last month's payment looks like It's just twelve dollars
of interest and two thousand three hundred eighty six dollars
of principle All of this is principal until well then
the balance is zero and we'll finally Then you will
have fully paid off your mortgage and own your home
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