How Many Calories Burned Sleeping 8 Hours? | Quick Math Guide

Calories Burned In Eight Hours Of Sleep: Formula And Examples

There’s a standard way researchers estimate energy burn across activities, including sleep. It uses metabolic equivalents (METs), where 1 MET is the energy cost of quiet rest, about 1 kilocalorie per kilogram per hour. In the adult compendium, the value for sleeping is 0.9 MET. Multiply that by body weight in kilograms and by hours spent asleep to get an estimate. In short: kcal = 0.9 × body weight (kg) × hours asleep.

Why 0.9? The Compendium of Physical Activities sets sleeping at the low end of intensity (0.9 MET), and academic references also frame 1 MET as ~3.5 mL O₂/kg/min, a standard way to tie oxygen use to calories. You can find both the sleeping MET range and the MET definition in peer-reviewed and university sources.

Quick Table: Eight Hours Across Common Body Weights

The chart below applies the 0.9 MET method to show an eight-hour window for a wide range of body sizes. Per-hour numbers help you scale to seven hours, nine hours, or any night you choose.

Body Weight	Calories In 8 Hours	Per Hour
45 kg (99 lb)	~324 kcal	~40 kcal
50 kg (110 lb)	~360 kcal	~45 kcal
55 kg (121 lb)	~396 kcal	~50 kcal
60 kg (132 lb)	~432 kcal	~54 kcal
65 kg (143 lb)	~468 kcal	~58 kcal
70 kg (154 lb)	~504 kcal	~63 kcal
75 kg (165 lb)	~540 kcal	~68 kcal
80 kg (176 lb)	~576 kcal	~72 kcal
85 kg (187 lb)	~612 kcal	~76 kcal
90 kg (198 lb)	~648 kcal	~81 kcal
100 kg (220 lb)	~720 kcal	~90 kcal
110 kg (243 lb)	~792 kcal	~99 kcal
120 kg (265 lb)	~864 kcal	~108 kcal

These values line up with what you’d expect from a resting-state estimate. If you compare that with calories burned while resting, sleep sits a bit lower per hour but follows the same weight-driven pattern.

How To Run The Numbers For Yourself

Step one: convert body weight to kilograms (pounds ÷ 2.2046). Step two: pick your sleep length. Step three: multiply 0.9 × kilograms × hours. That’s it. If you like a formula that starts from oxygen use, the standard conversion behind 1 MET uses 3.5 mL O₂/kg/min, which translates to kilocalories with a well-accepted constant used in exercise science.

Where The Formula Comes From

Researchers assign MET values to activities in a long-running compendium maintained in the scientific literature. Sleeping scores 0.9, while quiet sitting is 1.0. METs translate to calories with a simple equation many universities teach, and the compendium tables let you treat sleep the same way you’d treat walking, cycling, or housework in a calorie log. For a deeper look at the method, see a university explainer on the METs → calories formula and an academic update that lists the 0.9 MET for sleeping.

What Can Nudge Your Overnight Burn Up Or Down

Body mass sits at the center of the estimate, but a few levers can tilt the nightly total. You don’t need to memorize them; use them to understand mild swings around the table above.

Lean Mass And Body Size

Muscle tissue costs more energy to maintain than fat tissue. People with higher lean mass often see higher totals at any sleep length. That’s why two people at the same weight can still differ a bit—composition matters.

Age And Sex Differences

Aging tends to lower resting energy needs as lean mass changes. Men often show a higher absolute burn due to more lean mass on average, but the MET method still holds for anyone: weight × hours × activity MET.

Sleep Length, Stability, And Stage Mix

Eight hours isn’t magic; it’s a handy yardstick. Shorter or longer nights scale linearly in the math. In the lab, sleep metabolism drifts a little with stages, and the average across the night lands below quiet wakefulness.

How Sleep Compares To BMR And Quiet Rest

The overnight rate tends to sit a touch below classic basal measurements. Reviews of resting energy work often place sleeping metabolic rate around 5–10% lower than basal values, which is exactly why the 0.9 MET estimate maps cleanly to everyday calculators.

Worked Examples You Can Copy

Example 1: 62 kg Person, 7.5 Hours

kcal = 0.9 × 62 × 7.5 → 419 kcal. Round to the nearest 5–10 if you like tidy logs.

Example 2: 82 kg Person, 8 Hours

kcal = 0.9 × 82 × 8 → 590 kcal. If that same person sleeps 6.5 hours, it’s the same math: 0.9 × 82 × 6.5 → 479 kcal.

Example 3: Use A BMR-First Approach

Another route starts with a basal number, then trims it slightly for sleep. Many clinicians explain basal metabolic rate as the minimum energy the body needs for basic functions. If your basal estimate is 1,600 kcal/day, the hourly basal is ~67 kcal. During sleep, trim that by a small fraction and multiply by your sleep hours.

Reality Check: What These Calories Mean

Nighttime burn helps keep total daily energy balanced, but it won’t carry a weight-loss effort by itself. Those 360–720 kcal are already part of your daily total; daytime movement, steps, and training change the rest of the pie. Treat sleep as the stable base rather than a lever to push for extra burn.

Smart Ways To Use This Number

• Pick a fixed MET method (0.9) and keep it consistent in your log.
• Use the per-hour figure from the table to scale nights that run long or short.
• Pair the estimate with step tracking so your full-day picture isn’t missing movement.

Method Notes And Source Backing

METs are ratios. One MET corresponds to resting energy turnover, commonly tied to an oxygen-use reference of 3.5 mL/kg/min. The Compendium is the standard catalog researchers use to assign METs to common activities, with sleeping set to 0.9. University and medical sources outline how to convert METs to calories with a short equation, which is why you’ll see consistent math from fitness labs to classroom handouts.

You can read a journal-linked table that documents MET values and the definition of 1 MET on a university-hosted PDF. You can also see a .edu explainer that walks through the conversion from METs to kilocalories in plain language and includes worked examples. Both match the approach used in this guide and keep the math transparent.

Make The Estimate More Personal

Pick Your Preferred Path

There are two clean routes: the quick MET route in this article, or a basal-first method that starts from a personal basal estimate. If you lean on a basal calculator, remember that sleep sits a notch under quiet wakefulness. Reviews in sports science summarize that difference at roughly 5–10%, which maps to the 0.9 factor used here.

One Person, Three Assumptions (70 kg, 8 Hours)

Assumed MET / Ratio	What It Represents	Calories In 8 Hours
0.85 MET	Lower end vs. basal	~476 kcal
0.90 MET	Standard sleep estimate	~504 kcal
1.00 MET	Quiet wakefulness	~560 kcal

FAQ-Free Clarifications People Ask

Does Room Temperature Change The Number?

Within a comfortable range, not by much in everyday life. Shivering or heavy sweating would change energy needs, but standard bedroom conditions don’t swing totals enough to rewrite your log.

Does A Late Meal Raise Nighttime Burn?

Digesting food costs energy, yet most people finish dinner well before bedtime. The simple 0.9 MET method treats sleep itself, not mealtime spikes. If you often eat right before lights-out, your total daily energy will reflect that, even if the sleep slice in your log stays based on 0.9 MET.

What If My Tracker Shows Different Numbers?

Wearables use sensors and models that blend heart rate, movement, and sometimes temperature. They can be higher or lower than MET math on any given night. If you want consistency, pick one method and stick with it.

Sources You Can Trust

For the physiology: the Compendium series that anchors activity MET values and a university-hosted summary of MET definitions and oxygen conversion. For the basal perspective: a major health system’s overview of basal energy needs. These references align on the concepts behind the simple calculation method, and they keep your estimate grounded in accepted exercise science.

• A university PDF that explains 1 MET (~3.5 mL/kg/min) and provides research-based context: MET definition and context.
• A .edu guide that shows the calculation from METs to calories: METs to calories.
• A health-system primer on basal energy needs: Basal metabolic rate.

Practical Takeaway

Use 0.9 × kilograms × hours. Log the number once a week to keep your daily totals consistent. If you later switch to a basal-first method, apply a small trim to your hourly basal and multiply by your sleep time. Either way, keep the method steady so your trendlines tell a clear story.

Want a broader view of your day? Try our calories burned every day walkthrough.