# Calorie Deficit Calculator (TDEE + BMR) & Complete Guide

> Free calorie deficit calculator using Mifflin-St Jeor — get your BMR, TDEE, and recommended daily calories for losing or gaining weight.

Canonical: https://www.mycallie.app/en/guides/calorie-calculator
Published: 2026-05-19 · Updated: 2026-09-28
Author: Md Sadab Wasim · Source: https://www.mycallie.app

This calculator gives you a starting estimate for daily calorie targets. Plug in your numbers, get a target. The article below explains the math and how to adjust.

## The 30-second answer

**Daily calories to lose weight = TDEE minus 15–25%.** TDEE is your Mifflin-St Jeor BMR multiplied by an activity factor, from 1.2 (sedentary) to 1.9 (athlete). A moderately active 30-year-old woman at 165 cm and 65 kg has a BMR of about 1,370 kcal and a TDEE of about 2,124 kcal/day, so her loss target sits 15–25% below 2,124. Enter your own numbers in the calculator below, then adjust by 100–150 kcal after 2–3 weeks of weight data.

[Interactive calorie deficit calculator — use it on the page.]

## What is BMR?

**Basal Metabolic Rate (BMR)** is the energy your body burns to keep you alive at rest — breathing, circulating blood, maintaining body temperature, building and repairing cells. For most adults, BMR accounts for **60–75% of total daily calorie burn**.

The most validated formula for estimating BMR in healthy adults is the **Mifflin-St Jeor equation**:

> **Men:** BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
>
> **Women:** BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

For a 30-year-old woman, 165 cm, 65 kg: BMR ≈ (10×65) + (6.25×165) − (5×30) − 161 = 650 + 1031 − 150 − 161 = **1,370 kcal**.

## What is TDEE?

**Total Daily Energy Expenditure (TDEE)** is BMR plus the calories you burn from activity. It's the number you actually need to know for weight management.

The standard approach is to multiply BMR by an **activity multiplier**:

| Activity level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2 | Desk job, no formal exercise |
| Lightly active | 1.375 | Light exercise 1–3 days/week, or a job with light walking |
| Moderately active | 1.55 | Moderate exercise 3–5 days/week |
| Very active | 1.725 | Hard exercise 6–7 days/week |
| Athlete | 1.9 | Twice-a-day training or physical labor + training |

Most people **overestimate** their activity level. If you have a desk job and lift weights 3× a week, you're moderately active, not very active. Round down if you're unsure.

For our example (BMR 1,370, moderately active): TDEE ≈ 1,370 × 1.55 = **2,124 kcal/day**.

## Calorie deficit for weight loss

Eat below TDEE; lose weight. The classic estimate is that **3,500 kcal ≈ 1 lb (0.45 kg) of fat** — so a 500 kcal/day deficit produces roughly 1 lb per week.

This is approximately right early on but becomes less accurate as you lose weight, because BMR drops slightly with body mass. The [NIH Body Weight Planner](https://www.niddk.nih.gov/bwp) accounts for this adaptation.

**Recommended deficit ranges:**

| Deficit size | % below TDEE | Weekly loss (75 kg adult) | Trade-offs |
|---|---|---|---|
| Mild | 10–15% | 0.3–0.5 kg | Slow, sustainable, easy to adhere to |
| Moderate | 15–25% | 0.5–0.8 kg | The sweet spot for most adults |
| Aggressive | 25–35% | 0.8–1.2 kg | Faster but more muscle loss, more hunger |
| Crash | >35% | varies | Not recommended — high rebound risk |

A deficit so deep that your target calories drop below BMR almost always backfires. Your body downregulates non-essential systems (mood, libido, training quality, immune function) and you binge-rebound. If your TDEE - 25% lands below BMR, eat closer to BMR and lose more slowly.

## Calorie surplus for weight gain

Eating above TDEE supports weight gain. **For most adults, a 250–500 kcal/day surplus produces 0.25–0.5 kg/week gain.** If you're training for muscle gain, this range maximizes lean-mass gain and minimizes fat gain.

| Surplus size | % above TDEE | Weekly gain | Notes |
|---|---|---|---|
| Lean bulk | 5–10% | 0.1–0.25 kg | Slow, mostly lean mass if training |
| Standard bulk | 10–20% | 0.25–0.5 kg | The default for most lifters |
| Dirty bulk | 20–40% | 0.5–1.0 kg+ | Faster, more fat gain |

For weight gain, **what you eat matters more than for weight loss.** A 400 kcal/day surplus of donuts produces more fat than the same surplus from protein-rich whole foods. See our [healthy weight gain guide](/blog/healthy-weight-gain-guide) for specifics.

## Adjust based on actual results

The calculator gives a starting point. The truth comes from your bathroom scale.

After **2–3 weeks** on a target, check your weight trend:

- If you're losing **0.5–1% body weight/week**, your target is right.
- If you're losing **less than 0.3% body weight/week**, drop your target by 100–150 kcal.
- If you're losing **more than 1.5% body weight/week**, raise your target by 100–150 kcal. (Faster isn't better.)
- If you're gaining and want to be losing (or vice versa), recalculate — your activity level may have shifted.

Don't adjust based on a single day's reading. Daily weight fluctuates ±1 kg from water, food in transit, sodium, and hormones. Look at the **weekly average**.

## Why fitness-watch calories are usually wrong

Most popular fitness watches overestimate calorie burn from exercise by **20–40%**, according to multiple validation studies ([Shcherbina et al., 2017](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524096/)). Eating back "exercise calories" reported by a watch is a common reason people don't see the deficit they expect.

The activity multipliers in this calculator are derived from **doubly labeled water studies** — the gold-standard method for measuring TDEE — and tend to be more accurate than wearable-derived estimates.

## How Callie uses these numbers

When you set a goal in Callie, the AI calculates your TDEE using the same Mifflin-St Jeor approach and applies a deficit or surplus matched to your timeline. As you log meals and your weight trend updates, the target self-adjusts — so you don't have to recompute by hand. See our [guide to weight loss with a calorie tracker](/guides/how-to-lose-weight-with-a-calorie-tracker) for the full workflow.

## Sources

1. Mifflin MD, et al. (1990). "A new predictive equation for resting energy expenditure in healthy individuals." *Am J Clin Nutr* 51:241-247.
2. Frankenfield D, et al. (2005). "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults." *J Am Diet Assoc* 105(5):775-789.
3. Shcherbina A, et al. (2017). "Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort." *J Pers Med* 7(2):3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524096/
4. NIH Body Weight Planner. https://www.niddk.nih.gov/bwp
5. Hall KD, et al. (2011). "Quantification of the effect of energy imbalance on bodyweight." *Lancet* 378(9793):826-837.
6. Trexler ET, et al. (2014). "Metabolic adaptation to weight loss: implications for the athlete." *J Int Soc Sports Nutr* 11:7.

> **Important:** This calculator and guide are educational, not medical advice. If you have diabetes, are pregnant, have a history of disordered eating, or take medications that affect metabolism, consult a registered dietitian or physician before setting a calorie target.