BMI calculator
Calculate your BMI online using height and weight. Get body mass index results with metric and imperial units.
Free web browser tools
Health
Use standard formulas to produce general health estimates. These tools are informational and do not replace professional medical advice.
Calorie calculator
Estimate daily calorie needs based on age, height, weight, activity level, and goals.
Due date / pregnancy calculator
Estimate a pregnancy due date from the first day of your last menstrual period and see the estimated current gestational age. Uses the standard 280-day calculation.
TDEE calculator
Calculate your TDEE and BMR to find maintenance calories, plus targets to lose or gain weight. Mifflin-St Jeor or Katch-McArdle.
Body fat calculator
Estimate body fat percentage with the U.S. Navy tape-measure method. See fat mass, lean mass, BMI, and your fitness category.
Pace calculator
Calculate running pace, finish time, or distance in km or miles. Get race predictions for 5K, 10K, half marathon, and marathon plus splits.
Interval timer
HIIT and Tabata interval timer with work, rest, rounds, and sets. Beeps, voice cues, color-coded full-screen display.
Health FAQs
How are tags used on ReallyUseful.Tools?
Tags group tools by shared traits such as file converter, in browser, or privacy friendly so you can filter the directory by feature.