Built in bodyfat calculator from circumference measurments
Most clients do not have access/ability to measure bf. Electrical impedence devices are questionable and vary greatly based on many factors. Please allow the system to generate bodyfat based on entered circumference measurements. There are many formulas available. I have inserted the US Military and the even newer Ace (American Council on Exercise) formula below:
Military:
For men, use the following formula: % body fat = 86.010 x log10(abdomen  neck)  70.041 x log10(height) + 36.76 [8]
For women, use the following formula: % body fat = 163.205 x log10(waist + hip  neck)  97.684 x log10(height)  78.387
ACE:
For Men:
Before you use the formulas, there are two measurements that are required:
Measurement 1: Bodyweight
Measurement 2: Waist Girth (measured at the umbilicus)
Procedure:
1) Multiply your bodyweight by 1.082. Add the result to 94.42. Once your calculation is complete, save the number. à (Bodyweight x 1.082) + 94.42=Result 1
2) Multiply your waist girth by 4.15. Once you get this result, subtract it from the number obtained in step 1 (ie: Step 1 resultStep 2 result). The result obtained after the subtraction is done is your lean bodyweight (your weight if you had no fat in your body at all). à Result 1  (Waist Girth x 4.15)= Lean Body Weight
3) Finally, subtract your lean bodyweight from your total bodyweight (Total weightLean Bodyweight). Once you get the result, multiply that number by 100. Once you get the result divide it by your total bodyweight. This final result is your percentage of body fat. à ((Total Bodyweight  Lean Bodyweight) x 100) divided by (Your Body Weight) = Your Percentage of Body Fat.
Example:
I weigh 190 and I have a 30.5inch waist. Therefore, step 1 is (190 x 1.082) + 94.42 = 300. Step 2 says that my lean body weight equals 300(30.5 x 4.15)=173.425. Finally, Step 3 says that my body fat percentage is ((190173.425) x 100) divided by 190= 8.72%.
For Women:
Before you use the formulas, there are five measurements that are required (not fair, I know):
Measurement 1: Bodyweight.
Measurement 2: Wrist Circumference (measured at the widest point).
Measurement 3: Waist Circumference (measured at your umbilicus).
Measurement 4: Hip Circumference (measured at the widest point).
Measurement 5: Forearm Circumference (measured at the widest point).
Procedure:
1) Multiply your bodyweight by 0.732. à Bodyweight x .0732 = Result 1.
2) Add the result above to 8.987. à Result 1 + 8.987= Result 2.
3) Divide your wrist circumference by 3.14. à Wrist divided by 3.14 = Result 3.
4) Multiply your waist measurement by 0.157. à Waist x 0.157 = Result 4.
5) Multiply your hip measurement by 0.249. à Hip x 0.249 = Result 5.
6) Multiply your forearm measurement by 0.434. à Forearm x 0.434 = Result 6.
7) Add results 2 & 3. à Result 2 + Result 3 = Result 7.
8) Subtract Result 4 from Result 7. à Result 7  Result 4 = Result 8.
9) Subtract Result 5 from Result 8. à Result 8  Result 5 = Result 9.
10) Add Result 6 and Result 9. The result is your lean body mass (your fat free weight) à Result 6 + Result 9 = Lean Body Mass.
11) Subtract your lean body mass from your bodyweight. Once you get the result, multiply that number by 100. Once you get this result, divide it by your bodyweight. à ((BodyweightLean Body Mass) x 100) divided by your bodyweight.
Example:
A woman that weighs 125, and has a wrist measurement of 6.0, a waist measurement of 24, a hip measurement of 38, and a forearm measurement of 9.5 would calculate her body fat percentage in the following manner. Step 1: 125 x 0.732=91.5. Step 2: 91.5 + 8.987=100.487. Step 3: 6 divided by 3.14=1.91. Step 4: 24 x 0.157=3.768. Step 5: 38 x 0.249=9.462. Step 6: 9.5 x 0.434=4.123. Step 7: 100.487+1.91=102.397. Step 8: 102.3973.768=98.629. Step 9: 98.6299.462=89.167. Step 10: 4.123+89.167=93.29 (Lean Body Weight: Fat Free Weight). Step 11: ((12593.29) x 100) divided by 125 = (31.37 x 100) divided by 125 = 3171 divided by 125= 25.368 (Body Fat Percentage).

Amber Petrin commented
Much needed feature in the app. I have to manually calculate this for each client multiple times a month. This should be an easy formula to add in to give clients important data to monitor their continued progress.

Coach Nate commented
Would have thought this would be something that is very easy to add and is good for clients to be able to track.
Calipers are not something very useful for online clients but having a way to track body fat percentage loss would be good.... especially when you want to be able to tell a client to not worry too much about their scale weight. 
Ali Khashab commented
Automatic Body fat percentage calculation from girth measurements. Instead of using other apps to calculate it, we should get it immediately after typing down the client's measurements.
Please this is a must for our business.
Thanks in advance. 
Alex Sloan commented
The Navy has a very simple one that uses Height Weight Waist and Neck girth. Pretty accurate ~3% +/

Raissa Rangell commented
I think this should be a must have option for clients who do not have access to a caliber.
It just looks awful to have all those blank spaces for body fat when we are doing online coaching and can't be physically there to measure them.
I still can't believe this is a feature that it's not working yet.

Anonymous commented
From the body measurment the client is taking it would be great if Trainerize could automatically calculate body fat percentage.
If not, could you add waist size at the narrowest point & wrist at narrowest point.