Body fat percentage calculator template

Free build guide: Body fat percentage calculator for WordPress

This guide rebuilds the Body fat percentage calculator from this site in Gravity Forms: 12 inputs, 6 live results and no submit button. Expect about 54 minutes by hand. The template above is the same form as an import file, and the bundle adds a PDF version of this guide with a screenshot of every setting, plus the stylesheet.

You will end up with:

• Body fat (%)
• Body fat (%)
• Fat mass (lb)
• Lean mass (lb)
• Fat mass (kg)
• Lean mass (kg)

What you need

• Gravity Forms (any license) — Calculation fields and conditional logic are in core; log() needs GP Advanced Calculations.
• GP Advanced Calculations (Gravity Wiz) — Exponents, functions and date math in calculation fields. The formulas in this template use its syntax. Part of Gravity Perks; needs the Spellbook plugin active as well.

The formulas below use GP Advanced Calculations syntax: exponents, functions or date math that core calculation fields cannot do. Install and activate it, with its Spellbook parent plugin, before you start; without it every result shows 0.

1. Create the form

1. Go to Forms → New Form and name it Body fat percentage.
2. In Form Settings → Form Layout, set the CSS Class Name to fo-live-only. Step 3 uses it to hide the submit button.
3. Leave the form open in the editor; the fields come next.

2. Add the fields, in this order

Field IDs are assigned as you add fields. If yours come out differently, change the {Label:ID} references in the formulas to match your IDs. Settings not mentioned stay at their defaults.

1. Units · Radio Buttons · ID 1
Custom CSS Class (Appearance tab) fo-segmented.

Choices (tick show values and enter each value):

• in / lb — value us (selected by default)
• cm / kg — value metric

2. Sex · Radio Buttons · ID 2
Custom CSS Class (Appearance tab) fo-segmented.

Choices (tick show values and enter each value):

• Male — value 1 (selected by default)
• Female — value 0

3. Height (in) · Number · ID 3
Number Format 9,999.99; Default Value 70; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is in / lb..

4. Weight (lb) · Number · ID 4
Number Format 9,999.99; Default Value 180; Description “For the fat and lean mass figures.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is in / lb..

5. Neck (in) · Number · ID 5
Number Format 9,999.99; Default Value 15; Description “Just below the larynx, tape sloping slightly down at the front.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is in / lb..

6. Waist (in) · Number · ID 6
Number Format 9,999.99; Default Value 34; Description “Men: at the navel. Women: at the narrowest point.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is in / lb..

7. Hips (in) · Number · ID 7
Number Format 9,999.99; Default Value 38; Description “Women only: at the widest point.”; Conditional Logic (Advanced tab): Show this field if Units is in / lb and Sex is Female..

8. Height (cm) · Number · ID 8
Number Format 9,999.99; Default Value 178; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

9. Weight (kg) · Number · ID 9
Number Format 9,999.99; Default Value 82; Description “For the fat and lean mass figures.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

10. Neck (cm) · Number · ID 10
Number Format 9,999.99; Default Value 38; Description “Just below the larynx, tape sloping slightly down at the front.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

11. Waist (cm) · Number · ID 11
Number Format 9,999.99; Default Value 86; Description “Men: at the navel. Women: at the narrowest point.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

12. Hips (cm) · Number · ID 12
Number Format 9,999.99; Default Value 97; Description “Women only: at the widest point.”; Conditional Logic (Advanced tab): Show this field if Units is cm / kg and Sex is Female..

13. Body fat (%) · Number · ID 13
Number Format 9,999.99; Description “US Navy method, usually within 3–4 points of a scan. Men: 6–13% athletic, 14–17% fit, 18–24% average, 25%+ obese. Women: 14–20, 21–24, 25–31, 32%+.”; Custom CSS Class (Appearance tab) fo-result; tick Enable Calculation, Rounding 1; Conditional Logic (Advanced tab): Show this field if Units is in / lb..

( {Sex:2} * ( 86.010 * log( ( {Waist in:6} / 1 ) - ( {Neck in:5} / 1 ) ) - 70.041 * log( ( {Height in:3} / 1 ) ) + 36.76 ) + ( 1 - {Sex:2} ) * ( 163.205 * log( ( {Waist in:6} / 1 ) + ( {Hip in:7} / 1 ) - ( {Neck in:5} / 1 ) ) - 97.684 * log( ( {Height in:3} / 1 ) ) - 78.387 ) )

14. Body fat (%) · Number · ID 14
Number Format 9,999.99; Description “US Navy method, usually within 3–4 points of a scan. Men: 6–13% athletic, 14–17% fit, 18–24% average, 25%+ obese. Women: 14–20, 21–24, 25–31, 32%+.”; Custom CSS Class (Appearance tab) fo-result; tick Enable Calculation, Rounding 1; Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

( {Sex:2} * ( 86.010 * log( ( {Waist cm:11} / 2.54 ) - ( {Neck cm:10} / 2.54 ) ) - 70.041 * log( ( {Height cm:8} / 2.54 ) ) + 36.76 ) + ( 1 - {Sex:2} ) * ( 163.205 * log( ( {Waist cm:11} / 2.54 ) + ( {Hip cm:12} / 2.54 ) - ( {Neck cm:10} / 2.54 ) ) - 97.684 * log( ( {Height cm:8} / 2.54 ) ) - 78.387 ) )

15. Fat mass (lb) · Number · ID 15
Number Format 9,999.99; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 1; Conditional Logic (Advanced tab): Show this field if Units is in / lb..

{Weight lb:4} * ( {Sex:2} * ( 86.010 * log( ( {Waist in:6} / 1 ) - ( {Neck in:5} / 1 ) ) - 70.041 * log( ( {Height in:3} / 1 ) ) + 36.76 ) + ( 1 - {Sex:2} ) * ( 163.205 * log( ( {Waist in:6} / 1 ) + ( {Hip in:7} / 1 ) - ( {Neck in:5} / 1 ) ) - 97.684 * log( ( {Height in:3} / 1 ) ) - 78.387 ) ) / 100

16. Lean mass (lb) · Number · ID 16
Number Format 9,999.99; Description “Muscle, bone, organs, water.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 1; Conditional Logic (Advanced tab): Show this field if Units is in / lb..

{Weight lb:4} * ( 1 - ( {Sex:2} * ( 86.010 * log( ( {Waist in:6} / 1 ) - ( {Neck in:5} / 1 ) ) - 70.041 * log( ( {Height in:3} / 1 ) ) + 36.76 ) + ( 1 - {Sex:2} ) * ( 163.205 * log( ( {Waist in:6} / 1 ) + ( {Hip in:7} / 1 ) - ( {Neck in:5} / 1 ) ) - 97.684 * log( ( {Height in:3} / 1 ) ) - 78.387 ) ) / 100 )

17. Fat mass (kg) · Number · ID 17
Number Format 9,999.99; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 1; Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

{Weight kg:9} * ( {Sex:2} * ( 86.010 * log( ( {Waist cm:11} / 2.54 ) - ( {Neck cm:10} / 2.54 ) ) - 70.041 * log( ( {Height cm:8} / 2.54 ) ) + 36.76 ) + ( 1 - {Sex:2} ) * ( 163.205 * log( ( {Waist cm:11} / 2.54 ) + ( {Hip cm:12} / 2.54 ) - ( {Neck cm:10} / 2.54 ) ) - 97.684 * log( ( {Height cm:8} / 2.54 ) ) - 78.387 ) ) / 100

18. Lean mass (kg) · Number · ID 18
Number Format 9,999.99; Description “Muscle, bone, organs, water.”; Layout: half width, on the same row as its neighbor (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 1; Conditional Logic (Advanced tab): Show this field if Units is cm / kg..

{Weight kg:9} * ( 1 - ( {Sex:2} * ( 86.010 * log( ( {Waist cm:11} / 2.54 ) - ( {Neck cm:10} / 2.54 ) ) - 70.041 * log( ( {Height cm:8} / 2.54 ) ) + 36.76 ) + ( 1 - {Sex:2} ) * ( 163.205 * log( ( {Waist cm:11} / 2.54 ) + ( {Hip cm:12} / 2.54 ) - ( {Neck cm:10} / 2.54 ) ) - 97.684 * log( ( {Height cm:8} / 2.54 ) ) - 78.387 ) ) / 100 )

3. Hide the submit button

The results are live, so nothing needs submitting. Add this filter to your theme’s functions.php or a code-snippets plugin; it hides the button on any form carrying the fo-live-only class:

add_filter( 'gform_submit_button', function ( $button, $form ) {
	return str_contains( (string) rgar( $form, 'cssClass' ), 'fo-live-only' ) ? '' : $button;
}, 10, 2 );

Or with CSS alone: .fo-live-only_wrapper .gform_footer { display: none; }

4. Put it on a page and make it look like this

Add the form to any page with the Gravity Forms block, or the shortcode [gravityform id="X" title="false" ajax="false"]. The form inherits your theme’s styles; the classes you set in step 2 are hooks for the look you see on this site:

• fo-result on a calculation field makes it the big teal result panel.
• fo-result fo-result--sub makes the smaller secondary figures.
• fo-segmented on a radio field turns it into a segmented switch.
• Two fields on one row is the editor’s own column layout: drag a field beside another and the row splits in half. No CSS class is needed, and the old gf_left_half Ready Classes are deprecated.

The bundle includes the two stylesheets that implement those classes, with notes on matching your brand colors. Without them the form still works; it just looks like your theme’s default Gravity Forms styling.

How the math works is explained under “How it’s calculated” on the live Body fat percentage calculator.