BMR Reference for Age 20
Basal metabolic rate at age 20 is not one number — it is a range set by height and weight. This page holds the formula inputs steady at age 20 and sweeps body composition instead: four BMI levels, men at 175 cm and women at 165 cm, each estimated with both Mifflin-St Jeor and Harris-Benedict so the spread between the classic equations is visible at a glance.
Read the BMI-25 row as a worked example: 76.6 kg at age 20 returns 1765 kcal, 5 kcal below the 19-year figure of 1770. Harris-Benedict lands 76 kcal above Mifflin (4.3%), and moving from sedentary to extra active multiplies the same estimate out to 3,354 kcal — a 1,236 kcal swing next to the 310 kcal the age term costs between 18 and 80.
BMR at age 20 by body composition
| BMI | Men (175 cm) | Women (165 cm) | ||||
|---|---|---|---|---|---|---|
| Weight | Mifflin | Harris | Weight | Mifflin | Harris | |
| 20 | 61.3 kg | 1612 kcal | 1636 kcal | 54.5 kg | 1315 kcal | 1376 kcal |
| 25 | 76.6 kg | 1765 kcal | 1841 kcal | 68.1 kg | 1451 kcal | 1502 kcal |
| 30 | 91.9 kg | 1918 kcal | 2046 kcal | 81.7 kg | 1587 kcal | 1628 kcal |
| 35 | 107.2 kg | 2071 kcal | 2251 kcal | 95.3 kg | 1723 kcal | 1753 kcal |
From BMR to daily burn: TDEE at age 20
Multiplying BMR by an activity factor gives total daily energy expenditure. The factors below are the same five levels the main calculator offers, applied to the BMI-25 man from the table (76.6 kg, BMR 1765 kcal):
| Activity level | Factor | TDEE |
|---|---|---|
| Sedentary — little or no exercise | ×1.2 | 2118 kcal/day |
| Lightly active — 1–3 days/week | ×1.375 | 2427 kcal/day |
| Moderately active — 3–5 days/week | ×1.55 | 2736 kcal/day |
| Very active — 6–7 days/week | ×1.725 | 3045 kcal/day |
| Extra active — intense daily training | ×1.9 | 3354 kcal/day |
Get your own figure
Body size matters more than any reference table can capture, so a two-minute personal estimate is usually worth more than a row of averages. Enter your numbers and the box computes the Mifflin-St Jeor result with the same coefficients used across this site:
Frequently asked questions
What is the BMR of a 20-year-old?
It depends on body size as well as age. At age 20, a 175 cm man weighing about 76.6 kg has a Mifflin-St Jeor BMR of roughly 1765 kcal per day, while a 165 cm woman at 68.1 kg lands near 1451 kcal per day. The table above shows how the estimate moves across four common body-composition levels.
Why does BMR fall as age increases?
The Mifflin-St Jeor equation subtracts 5 kcal for every year of age, so between age 20 and age 80 the estimate drops by about 300 kcal per day at the same height and weight. The coefficient is a population average: body composition, not the birthday itself, drives most of the real change.
Mifflin-St Jeor or Harris-Benedict — which should I use?
Mifflin-St Jeor is the default on this site because validation studies found it tracks measured resting energy expenditure more closely for most adults. Harris-Benedict, shown beside it in the table, runs higher for many people — often by 5 to 10 percent — so comparing the two columns is a quick way to see the uncertainty band around any single number.
Nearby ages
Want the full picture — Katch-McArdle from body-fat percentage, the age chart and TDEE in one run? Open the BMRScope calculator or browse every age page.