Gravity Forms
+ Measurement Field (Unit Conversion)

A Number field takes one number with no unit. A visitor who knows their height in feet and inches has to work out centimetres first, a flooring quote priced per square metre cannot take square feet, and a parcel form in kilograms loses every customer who weighs in pounds. The Gravity Forms Measurement Field add-on lets each visitor use the unit they know and gives you one consistent unit on every entry.

Add a Measurement field and choose what it measures: length, body height, weight, area, volume or temperature. Tick the units visitors may use, pick the unit shown first and the base unit stored on the entry. Visitors switch units from a list; feet and inches, stones and pounds and pounds and ounces get two boxes, and the value already typed is converted when they change unit. A short line under the field shows the value in your base unit as they type.

Every conversion uses the exact legal definitions (1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 US gallon = 231 in³, 1 UK gallon = 4.54609 L). The server reads only the numbers typed and the unit chosen, converts them again and checks them, so a value changed in the browser is never stored. Set a minimum and maximum in any unit — for example 4.5 ft to 2.2 m — and visitors see the limits in their own unit. The entry keeps the base value and what the visitor typed, shown on the entry screen and exported as its own column. Use {Height:3:cm}, {Height:3:ft_in} or {Height:3:display} in notifications, {Area:4:m2} in Number-field calculations and product prices, and conditional logic on the base value. An optional BMI helper works out the body mass index from a height and a weight field. Everything runs on your own server: no outside connection. For Gravity Forms 2.9 and newer.

The field shows a number box (or two boxes for feet and inches, stones and pounds, pounds and ounces) and a unit list. As the visitor types, the browser converts the value into the base unit with the same exact factors and the same rounding the server uses, and puts it in a hidden value that Gravity Forms calculations and conditional logic read. When the form is submitted, the add-on ignores that hidden value: it reads the typed numbers and the unit, checks that the unit is one you allowed, that the numbers are numbers, that inches are under 12 and that a temperature is not below absolute zero, converts the value into your base unit, checks the minimum and maximum, and stores the base value as the field value. What the visitor typed and the unit they chose are kept as entry meta for the entry screen, merge tags and the CSV export. Everything happens on your own server — the add-on makes no outside HTTP request beyond the licence and update checks.