# Calories to lose weight: a moderate deficit

> A moderate calorie deficit means eating 10% to 20% below daily burn (TDEE). A 30-year-old man who is 5 ft 11 in and weighs 180 lb, moderately active, burns about 2,788 calories. At a 15% deficit, the target is 2,370 calories, 418 fewer a day. Without medical supervision, women should not go below 1,200 calories and men not below 1,500.

Source: https://www.calterix.com/en-us/calculator/calorie/calories-to-lose-weight/ · Updated 11/06/2026 · en-US

## How the deficit is calculated

The starting point is **total daily energy expenditure** (TDEE): Mifflin-St Jeor BMR times an activity factor, as in the [calorie calculator](https://www.calterix.com/en-us/calculator/calorie/). The deficit is a percentage of daily burn, capped at 20%. BMR is the base of the math, and daily burn is the result after the activity factor.

```
Target = daily burn × (1 − deficit)
Pace (lb per week) = daily deficit × 7 ÷ 3,500
```
Example: daily burn of 2,788 and a 15% deficit. Target = 2,788 × 0.85 = 2,370 calories. Daily gap = 418, about 0.8 lb per week.

| Deficit | Target for a burn of 2,400 | Gap per day |
| --- | --- | --- |
| 10% | 2.160 calories | 240 calories |
| 15% | 2.040 calories | 360 calories |
| 20% | 1.920 calories | 480 calories |

Sample numbers for a daily burn of 2,400 calories.

## Safety limits

- Floor of 1,200 calories for women and 1,500 for men. Going below needs a doctor or registered dietitian. The calculator never suggests a target below the floor.
- Losing weight too fast raises the risk of muscle loss, gallstones, and low nutrient intake.
- Skip this tool during pregnancy or nursing, under age 18, with a history of eating disorders, or with conditions like diabetes, unless a professional guides you.

Before picking a goal weight, check your [BMI](https://www.calterix.com/en-us/calculator/bmi/) and the [ideal weight](https://www.calterix.com/en-us/calculator/ideal-weight/) range for your height. Resting burn is explained in the [BMR calculator](https://www.calterix.com/en-us/calculator/bmr/).

## The 3,500 calorie rule

The rule says a pound of body fat holds about 3,500 calories, so a 500 calorie daily deficit means roughly a pound a week. The math gives a ballpark but overstates real loss: metabolism slows as weight drops, some lost weight is water and lean mass, and people slip.

That is why the **pace and timeline** tab shows a theoretical timeline. Real progress tends to be slower and uneven. Judge it by multi-week trends, not by single days.

> This page does not prescribe a diet or promise weight loss. The result is a reference calculation.

## Frequently asked questions

### How many calories should I eat a day to lose weight?

Typically 10% to 20% below daily burn, with a floor of 1,200 calories for women and 1,500 for men. At a burn of 2,788 calories, a 15% deficit is 2,370 calories.

### What is a safe calorie deficit?

A moderate deficit, 10% to 20% of daily burn or about 250 to 750 calories a day, is usually well tolerated by healthy adults. Larger deficits call for professional supervision.

### How do I figure out my calorie deficit?

Estimate daily burn (BMR times an activity factor), then subtract the deficit percentage. With a burn of 2,788 and a 15% deficit, the target is 2,788 × 0.85 = 2,370 calories.

### How much weight can I lose in a week?

By the 3,500 calorie rule, a 500 calorie daily deficit works out to about 1 lb a week. Real results vary, and losing more than 1% of body weight a week needs medical oversight.

### Is it OK to eat less than 1,200 calories a day?

Only with a doctor or registered dietitian watching. Very low calorie diets without supervision raise the risk of nutrient gaps and muscle loss.

### Does this calculator count calories in food or plan a diet?

No. The tool sets a daily energy target for reference, not a menu. Food calories are on the Nutrition Facts label, and a registered dietitian can build a plan around your needs.