Buying Half Points in Football

A statement repeated on betting forums often is “if buying
half-points were +EV the bookmaker wouldn’t sell them”. This
is just another football betting myth. In this article I’ll discuss buying
half-points for NFL football betting in great depth, touch on
college football, and teach you easy to follow
football betting strategy for buying half-points.

Buying Half Points Explained

Most online betting sites (Bovada being the exception) allow
bettors to purchase half-points from a point spread starting at
10-cents each. So for example, if the point spread is -6.5 -110
you can purchase a half-point bringing it to -6.0 -120, or 2
half-points bringing it to -5.5 -130. If the point spread is
+4.5 -105 you can purchase to +5.0
-115 or +5.5 -125. Now there are some exceptions to this.

The Value of Half Points

Finding the fair value of a
half-point purchase requires two things 1) a push chart and 2)
trivial mathematics. The table to the left is a push chart I
created for NFL football; I’ll discuss push charts briefly later
in this article. As far as the math goes we’ll need to first
calculate our implied probability using the formula
risk/return=implied probability, where return is stake+win. For
example: -110 is risk $110 to win $100; the return is $210 ($110
stake + $100 win). So for -110 the implied probability is
110/210=0.5238 or in other words 52.38%. This tells us at odds
-110 we need to win 52.38% of the time to break even.

Calculating the value of a half-point buy is now a matter of
simple mathematics, so long as we already have a push chart.
Considering we have one, let’s a take a look at the value of
moving a point spread from +6.5 -110 to +7.0. On the NFL push
chart I just provided you’ll see the favorite wins by 7 points
5.7% of the time. Now considering at +6.5 we lose on a -7
outcome, and now we push at -7 we’re going to take half the 5.7%
probability and add it to the 52.38% implied probability of
-110.

Why only half? If we were moving from +6.5 to +7.5 we would
take the full 5.7% value. However moving +6.5 to +7.0 we can
only take half because on that number we push not win. Our
opponent (the bookmaker) who has -7.0 also pushes. So half the
5.7% is in his -7.0 line, and half the 5.7% is in our line of
+7.0. The same would be true moving +7.0 to +7.5; we take half
the push probability of 7, because we’re going from a push on 7
to a win on 7. Our increase is half the probability. When
dealing with half points we’re always either moving off a push
(and therefore take half the probability of the number we move
off of) or onto a push (and therefore take half the probability
of the number we move on to).

So in this case of +6.5 to +7.0, half of 5.7% is 2.85%. We
add this 2.85% to the +6.5 -110 implied probability 52.38% to
get a new +7.0 implied probability of 55.23%. If you go to our

odds converter and plug 55.23% into the implied probability
field you’ll see in American odds this is -123. This tells us
moving +6.5 -110 to +7.0 is worth 13 cents. It also tells us
that +6.5 -110 and +7.0 -123 have the same expected value.

An Important Lesson

When moving -110 to -123 the line moved 13 cents. I want to
make it clear that cents are a meaningless evaluation figure. To
best illustrate why, please allow me to exaggerate the point. We just
showed that increasing a 52.38% probability 2.85% moves the
American line 13 cents. Let’s say however the line was +6.5
-280, which is risk $280 to win $100. Using Risk $280 / Return
$380 = Implied Probability we see the implied probability of
-280 is 73.68%. If we add 2.85% to this we get a new implied
probability of 76.53. Go to our odds converter, plug in 76.53%,
and you see this is American odds -326. So the same 2.85%
increase in this case moved -280 to -326, and therefore was worth
46 cents, not 13 cents.

The lesson I’m attempting to give is the value of half points
are progressive. If the line starts at -105 the value of a half
point is less than if it started at -110; if the line starts at
-115, then it’s worth more. Likewise, when making multiple-half point
purchases each half point purchased has greater value than the
last. If betting sites didn’t limit the number of half point we
could buy at 10 cents each, we could purchase a ton of them to
the point all bets we make are +EV. I’ll come back to +EV
half-point buys in a bit, but first let me cover the best betting
sites for purchasing half points.

Best Betting Sites for Half Point Purchases

For the most part any betting website selling half-points at
25-cents for point spreads involving +3/-3, 15-cents for point
spreads involving +7/-7 and 10 cents for all other point spreads
is ideal. However, there are small little intricacies that make
some sites more ideal than others.

BetOnline.com – While many online betting sites only allow
bettors to purchase two or three half points at 10-cents each,
BetOnline actually allows punters to purchase four. Remember the
lesson earlier, because the value of half points is progressive
each one you purchase is worth more than the last. So the fact
that they sell four for 10 cents can be a huge plus. They also only
charge 15-cents (instead of 25 cents) on college football point
spreads involving +3/-3, and also don’t charge a premium on the
+7/-7 for college football either, offering 10 cents instead of
the 15 cents many other sites charge.

JustBet.com – Although not as ideal as BetOnline, JustBet is
decent for half point purchases. Here you can purchase
3-half-points maximum at 10 cents each, and they charge just 20
cents for the three on college football.

TopBet.com – Topbet ranks #1 on our list of
sports betting bonuses, but when it comes to half point buys
here you’ll want to stick to only purchasing a maximum of 2
half-points or buying 5 or 6. This is because at TopBet the first
two cost 10 cents each and the remainder cost 15 cents each.
This makes buying 3 or 4 poor value, but buying 5 or 6 will
often offset the loss in value.

5Dimes.com – 5Dimes is the nuts when it comes to half point
buys. This is because they price half points unique depending on
which point spread you’re crossing. They also allow bettors to
purchase them unmatched in the industry 10-20 half-points per
game. They are a reduced juice sportsbook, and you’ll
quite often find the best value here.

I should note that while we love them for their great odds on
football teasers, Bovada.lv isn’t a good site for buying
half points. This is because very rarely do they even offer the
option, and when they do it’s only on low value numbers such as
buying +8.5 in NFL to +9. If you use them for other reasons,
just avoid their half point buys.

Buying Half Point Strategy

I’ve already covered how buying half-point works and how to
calculate their value, but I haven’t discussed push charts. It’s
worth noting that season to season NFL push charts don’t change very
much and mine was last calculated going into the 2012/13 season,
so it should be good for at least a few years. When dealing with
college football you have two options #1 create a push chart, or
#2 remove vig from Pinnacle Sports.

Proof Buying Half Points Can be +EV

Let’s take case of a point spread that’s +9.5 -110. As
already covered earlier in this article the implied probability
of -110 is 52.38%. I also provided a push chart that showed
-10/+10 pushes about 4.9% of the time. If we decided to purchase
two half points bringing the line to +10.5, our implied
probability is 52.38%+4.9%=57.28%. If we plug this new
percentage into our

odds converter we see in American odds format this is -134.
If the bookmaker was charging the fair price for +9.5 to +10.5
he’d charge us -134, yet every betting site I know of sells
half points moving from +9.5 to +10.5 which costs just -130. If we
already thought +9.5 -110 was a neutral or better value bet,
we’d be foolish not to purchase two-half points here because doing
so lowers the bookmaker’s advantage.

Now considering 14 also has a 4.9% probability we can now
determine the following 4-half point buys are always must
purchases.

1. When betting +9.5 -110 always buy to +10.5 -130
2. When betting -10.5 -110 always buy to -9.5 -130
3. When betting +13.5 -110 always buy to +14.5 -130
4. When betting -14.5 -110 always buy to -13.5 -130

Although these are the best half point buys there are others.
Let’s take the example of a point spread +6 -115. The implied
probability of -115 is 53.49%. If we were to buy this to +7.5 we
would take half the probability of 6 which is 3.4%/2=1.7% and
the full probability of 7 which is 5.7%. So, 53.49%+1.7%+5.7%=
60.89%. Using our odds converter we can see that 60.89% is -155.6 in American
odds format. At betting sites the move +6.0 to +6.5 would cost
10 cents where the next two cost 15 cents each, because they
involve the seven. So, 110+10+15+15=150; the betting site is
giving us -150 when we just calculate the fair price for the
extra points should have been -155.6.

To conclude, let me mention there’s still vig in the initial
lines of all these examples. However, in these spots buying half
points did lower the bookmaker advantage. If the lines was
already a +EV bet we made it better. Perhaps if it was slightly
-EV and we were on the fence we could make it +EV with the half
point purchase. The reason these numbers work is because I’m
dealing with common margins of victory and also purchasing
multiple half points (which remember each one you purchase has a
higher value than the last). You’ll want to avoid low value
numbers. When it comes to half-point buying, our target numbers
of 7, 10, 14, 17, and 21. If we can use multiple half points to
cross these numbers more times than not we’re increasing the
value of our wager.

This concludes my article on buying half-points in football.
If you’ve read this article in full, understand it, and are
interested in buying half points for value I suggest also
reading the following articles:

• 
  NFL Teaser Strategy
• 
  College Football Teasers
• 
  Pleaser Betting Guide