BMR Reference for Age 39
Basal metabolic rate at age 39 is not one number — it is a range set by height and weight. This page holds the formula inputs steady at age 39 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.
Held at the same 76.6 kg, the age-38 page reads 1675 kcal against the 1670 here — 5 kcal below, which is exactly the 5 kcal the Mifflin-St Jeor age term removes per birthday. Harris-Benedict sits 63 kcal higher on that row, a 3.8% band. Across the five activity levels the same body spans 2,004 to 3,173 kcal — 1,169 kcal, against just 310 kcal that the age term strips out between 18 and 80.
BMR at age 39 by body composition
| BMI | Men (175 cm) | Women (165 cm) | ||||
|---|---|---|---|---|---|---|
| Weight | Mifflin | Harris | Weight | Mifflin | Harris | |
| 20 | 61.3 kg | 1517 kcal | 1528 kcal | 54.5 kg | 1220 kcal | 1294 kcal |
| 25 | 76.6 kg | 1670 kcal | 1733 kcal | 68.1 kg | 1356 kcal | 1420 kcal |
| 30 | 91.9 kg | 1823 kcal | 1938 kcal | 81.7 kg | 1492 kcal | 1545 kcal |
| 35 | 107.2 kg | 1976 kcal | 2143 kcal | 95.3 kg | 1628 kcal | 1671 kcal |
From BMR to daily burn: TDEE at age 39
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 1670 kcal):
| Activity level | Factor | TDEE |
|---|---|---|
| Sedentary — little or no exercise | ×1.2 | 2004 kcal/day |
| Lightly active — 1–3 days/week | ×1.375 | 2296 kcal/day |
| Moderately active — 3–5 days/week | ×1.55 | 2589 kcal/day |
| Very active — 6–7 days/week | ×1.725 | 2881 kcal/day |
| Extra active — intense daily training | ×1.9 | 3173 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 39-year-old?
It depends on body size as well as age. At age 39, a 175 cm man weighing about 76.6 kg has a Mifflin-St Jeor BMR of roughly 1670 kcal per day, while a 165 cm woman at 68.1 kg lands near 1356 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.