FOC calculator header image

FOC Calculator | Easily find Front-Of-Center of your hunting arrows

If you already know the length and balancing point of your arrow, you can use the FOC Calculator below to quickly find the % of your arrow’s weight that is Front-Of-Center! (enter a number or slide the orange dots to the desired number)

FOC (Front Of Center) | Calculator
Arrow length from end of arrow shaft to the bottom of the nock groove (L)
inches
Distance from balance point to the bottom of the nock groove (A)
inches
FOC (Front Of Center):

0 %

You may have heard other bowhunters talk about the “FOC” of their hunting arrows. (Who knows, you may have even heard “The Ranch Fairy” ranting about high FOC).

But, what does “FOC” mean and how can you easily calculate it?

Also, check out our Arrow Speed Calculator here!
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What does FOC stand for?

“FOC” stands for Front-Of-Center (Or Forward-Of-Center) and refers to the percentage of an arrow’s overall weight that is forward of the balancing point, or, “center” of the arrow.

Kinetic Energy Calculator (momentum too!)

How to calculate FOC using a formula

You might like the FOC calculator but also want to learn how to calculate FOC using a formula.

The formula to calculate an arrow’s FOC is:

100 x (Balance Point measurement [A] – Arrow Length [L]) / 2.

To use this formula, you will first need to measure the arrow’s overall length as well as finding the balance point measurement.

foc equation graphic
Once you have found the arrow length (A) and balance point (B) measurements, use the formula above to find the FOC of your hunting arrow.

Finding the arrow’s length

To find your arrow’s length for the purposes of calculating FOC, you need to be sure you measure correctly.

Measure your arrow from the end of the arrow (where the broadhead/point screws in) to the bottom of the throat of the nock (see diagram above).

Once you have your arrow length measurement, you need to measure the balancing point…

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How to find the “balance point” of an arrow

To find the balance point of your hunting arrow, first be sure you have already installed your nocks, vanes, inserts and broadheads/points onto your arrow.

balance point FOC diagram
To calculate FOC, you first need to find the “balance point” of your hunting arrow.
Learn how nock tuning will improve your arrow flight

Using a triangular block of wood, find the exact place that your arrow balances perfectly. (If you don’t have a triangular block, you can also balance the arrow on your finger).

Once you have found the balance point of your arrow, measure from that point to the throat of your nock. This will be your balance point measurement.

Lighted nocks on the cheap [DIY!]

Conclusion

Once you have measured your arrow’s length and balancing point, you can use the formula provided in the diagram above to calculate the FOC of your arrow.

Certainly bowhunters want to be the best they can be so that they can get an ethical kill. But, when it comes to FOC, there are varying opinions on whether higher or lower FOC is better.

Some bowhunters want a lighter overall arrow weight, so that the arrow is as fast as possible. The intent is often to keep the deer or other game from “ducking the string.”

The desire for a lighter arrow is often why some hunters don’t want a “higher FOC” arrow (since adding more weight to the front of the same arrow, with inserts or heavier broadheads would increase FOC, but also slow the arrow down.)

tuffhead broadheads

Consider heavier broadheads and/or inserts when seeking a higher FOC. An arrow with an FOC of 8-12% FOC could be considered “normal,” while a “high FOC” arrow would start around 15% and can go up to even 30%.

Others want an arrow that has a higher FOC %, (you may have seen The Ranch Fairy discuss this) so that the arrow hits the animal with a heavier impact. This can increase the odds of a “pass-through” shot. It can also help increase the chances of a mortal wound in the event you encounter bone or other stiff tissue that might impede the arrow’s progress.

Hopefully you find our FOC calculator helpful and we hope you have an arrow that’s Just Pass’N Through!

bow hunting tips picture of man with bow and arrow

Draw length made easy [draw length calculator!]

Are you wondering how to determine the draw length you need for bowhunting? Check out our draw length calculator below to easily and quickly determine it!

Draw Length Calculator
Wingspan (take a measurement of your wingspan between the fingertips of your middle fingers)
move slider or enter value
inches
Draw Length:

What is draw length?

With traditional bows, you can basically pull back as far as you are able, based on the draw weight of that particular bow. The same is true for a recurve bow.

bare shaft tuning arrows through paper when arrow building

Draw length is an extremely important component to good form and repeatable shot mechanics.

However, you will typically find that draw length is discussed in regards to compound bows. This is because a compound bow has a set maximum draw length, once you hit the “back wall” of the draw cycle (the back wall is the place in the draw cycle where you can no longer pull the bow any farther.)

Expand your broadhead selection knowledge

How to find your draw length

Time needed: 1 minute

If you don’t want to use the N1 Outdoors draw length calculator above and instead want to figure your estimated draw length with good ‘ole mathematics, the first thing you need to do is measure your armspan (or wingspan).

  1. Spread out

    First you need to determine your armspan. Simply spread out your arms (don’t over-stretch) with your palms facing forward.

  2. Measure

    Measure the distance from the tip of one middle finger to the tip of the other middle finger.man measuring armspan for bowhunting

  3. Do some old school calculating

    Take the measurement from step 2 and divide it by 2.5. This will provide you with a fairly reliable estimate of your appropriate draw length. Check with your local bow shop to help you fine tune.

Want to know the FOC of your hunting arrows? It’s FAST!
Learn how to be an arrow building ninja!

Here’s what the Archery Manufacturer’s and Mechants Organization (now the Archery Trade Association) says about draw length:

“Draw length is a specified distance, or the distance at the archer’s full draw, from
the nocking point on the string to the pivot point of the bow grip (or the theoretical vertical projection of a tangency line to the pivot point parallel to the string)
plus 1 3/4”. Draw length from pivot point shall be designed at DLPP and shall be
called TRUE DRAW LENGTH.
EXAMPLE: 26 1/4” DLPP plus 1 3/4” is the equivalent of 28” draw”

AMO Standards Committee FIELD PUBLICATION FP-3, 2000

So, by this definition, if you have a “28-inch draw length”, that means that at full draw the distance from the deepest point of the grip to the nocking point of the string would be 26.25 inches.

Check out this awesome Kinetic Energy and Momentum Calculator!

Draw Length vs. Arrow Length

It’s important not to confuse draw length with arrow length. While they may be similar lengths, they are measured differently.

Arrow length is measured from the front end of the arrow shaft (not including the broadhead or field point) to the throat of the nock.

Your arrow length can vary depending on what you are trying to achieve regarding the FOC and spine of your arrow. (Spine is how much your arrow flexes at a set length with a set weight attached. More on arrow spine here.)

how to measure arrow length

Arrow length is the measurement from the end of the arrow shaft to the throat, or groove, of the arrow’s nock.

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What is “full draw?”

When it comes to archery and bowhunting in regards to compound bows, “full draw” is when you have reached the farthest point that the bow can go in the draw cycle, reaching your anchor point.

What is an “anchor point?”

The “anchor point” is a reference point for an archer or bowhunting that they can “anchor” the bow string or the shooting hand when they are at full draw.

An anchor point helps make the archer’s shot repeatable, so that shot consistency can be achieved.

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Learn how to be a deer hunting ninja!

For example, many bowhunters will anchor the knuckle of their index finger just below their ear lobe behind the jaw.

Others may use a “kisser button,” (of all the parts on a bow, this might be the most memorable) which is usually a small disc that is installed on the bow string, above the nocking point.

man shooting compound bow at target

Many bowhunters will use an anchor point just below the ear, resting the knuckle of the index finger in the area right behind the jaw.

Learn how to nock tune your hunting arrows FAST!

Conclusion

As you can see, draw length measurement is a critical part of becoming a good archer. We hope this article and our draw length calculator has been helpful to you!

man shooting compound bow at target

Bow And Arrow Speed Calculator | FAST results!

Looking to get an estimate of your bow’s arrow speed based on your bowhunting setup? Try our arrow speed calculator below!

Arrow Speed Calculator
Bow Manufacturer IBO Speed
move slider or enter value
ft/sec
Draw Weight
move slider or enter value
lbs
Draw Length
move slider or enter value
inches
Arrow Weight
move slider or enter value
grains
Weight Added to String (20gr=peep only, 45gr=peep and tube)
move slider or enter value
grains
Estimated Arrow Speed:
/

Use the tool above to calculate the speed of your arrow!

When it comes to archery, IBO stands for International Bowhunters Organization.

What is IBO Speed and how is it calculated?

You might have seen where compound bows have an IBO rating.

But, what does that really mean?

Well, the IBO speed of a bow is calculated using a bow with a draw weight of 70 lbs, a draw length of 30 inches, and an arrow weight of 5 grains per pound of draw weight. So, that would mean a 70-lb draw weight would be shooting an arrow that weighs 350 grains (70 x 5 = 350).

That arrow is then shot through that bow through a chronograph, which measures the arrow speed. The average speed becomes known as the IBO rating of that particular bow.

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The problem with IBO ratings

The problem with IBO ratings, however, is that they are not typical of most hunters’ setups.

For example, a 30-inch draw length is rather long for the average archer. Also, an arrow weight of 350 grains is simply not typical of most hunting setups. And, with high FOC arrows gaining popularity, the arrow’s grains per inch is often significantly greater.

FOC Calculator for bowhunters!

So, when using the arrow speed calculator above, you must understand that the IBO rating you enter is based on this premise. The calculator will give you an estimate of how changing the inputs that make up IBO could affect your arrow speed.

The arrow speed calculator makes the following assumptions:

  • Every inch of draw length under 30″ will subtract 10 ft per second from the IBO value.
  • Every inch of draw length above 30″ will add 10 feet per second to the IBO value.
  • Every 3 grains of total arrow weight above draw weight multiplied by 5, will subtract 1 foot per second from the IBO value.
  • Every 3 grains of additional weight on the bow string will subtract 1 foot per second from the IBO value.
Kinetic Energy Calculator for bowhunters
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Other Inputs for Arrow Speed Calculator

After you have entered your bow’s manufacturer rated IBO, enter the following information:

  • The draw weight of your bow in pounds.
  • The draw length of your bow in inches
  • The arrow weight in grains (includes fletchings, wraps, inserts and also points/broadheads
  • Total string accessory weights in grains (peep, tube, silencers, etc.). For your reference, an estimated peep only weight is 20 grains, and a peep + tube is 45 total grains.
Why Iron Will Broadheads are a fixed-blade favorite

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