If you run a fitness website with an international audience — and virtually all WordPress sites do — you need fitness calculators that support both metric and imperial units. Forcing users to convert manually before using a calculator is a significant friction point that costs you engagement and credibility.
The Global Split
The United States, Liberia, and Myanmar are the only countries that officially use the imperial system. Everyone else — the UK for many measurements notwithstanding — uses metric. However, US fitness audiences are large and highly engaged, and US users are deeply accustomed to pounds and feet. A calculator that only accepts kilograms and centimetres will lose a significant portion of its potential audience.
Why Unit Conversion Matters More Than You Think
Research on usability consistently shows that forcing users to perform mental arithmetic before interacting with a tool significantly increases abandonment rates. A visitor who wants to know their BMI but has to first convert 165 pounds to kilograms and 5’8″ to centimetres will often just leave. The friction is small but real, and at scale it costs traffic and trust.
How FitNFO Handles Units
Every FitNFO calculator includes a metric/imperial toggle. Users switch units with a single click — weight converts between kg and lb, height converts between cm and ft/in, distance converts between km and miles. All conversions happen instantly with no page reload. The user’s preference is remembered for the session.
Give Your Visitors the Best Calculator Experience
FitNFO supports metric + imperial on all 130 calculators.