July 19, 2026 · CalorieToday Team

How Many Calories to Lose Weight? A Practical Guide

Weight loss comes down to a calorie deficit, but "how many calories should I eat" has a more nuanced answer than any single number. Here's how to estimate a deficit that actually works, and how to tell if you've overshot it.

The energy balance concept

At its core, weight change is governed by energy balance: calories in versus calories out. Eat roughly the same number of calories your body burns (your TDEE, or Total Daily Energy Expenditure) and your weight stays stable. Eat consistently less than that and you lose weight. Eat consistently more and you gain. This isn't a theory you can opt out of — it's how energy conservation works in a biological system — but it's also not the whole story, because the "calories out" side of the equation isn't fixed. It shifts in response to what you eat, how much you sleep, your stress levels, and how long you've been dieting.

How to estimate your TDEE

Before you can set a sensible calorie target, you need a starting estimate of how many calories you burn in a day. The most common approach uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR) — the calories you'd burn at complete rest — and then multiplies that by an activity factor to account for movement and exercise. You can get this number instantly with our free TDEE calculator, which uses the same formula and activity tiers built into the CalorieToday app.

Treat the result as a starting point, not gospel. Formula-based estimates are typically accurate within about 10% for most people, but individual metabolism varies. The real value comes from tracking your actual intake and weight over a few weeks and adjusting from there — which is a big part of what a tracking app like CalorieToday is for.

Why a moderate deficit beats an aggressive one

Once you have a TDEE estimate, the next question is how big a deficit to run. A commonly recommended starting point is around 500 calories per day below TDEE, which corresponds to roughly 1 pound of weight loss per week. There's nothing magic about 500 specifically — it's simply a deficit large enough to produce a noticeable, motivating rate of loss, while usually being small enough to sustain without constant hunger, fatigue, or a spiraling relationship with food.

Aggressive deficits (cutting 1,000+ calories a day, or dropping to very low absolute intakes) can produce faster short-term results, but they come with real costs: they're harder to sustain, they increase the risk of losing lean muscle mass alongside fat, and they tend to trigger stronger hunger and cravings that make rebound overeating more likely. A moderate, sustainable deficit that you can actually maintain for months will usually beat an aggressive one that collapses after two weeks.

Realistic weekly loss rates

As a general guide, most sources suggest:

• 0.5 lb/week — a gentle deficit, well suited to people with a smaller amount of weight to lose, or anyone prioritizing sustainability and muscle retention above speed.
• 1 lb/week — a moderate, widely recommended default for most people with weight to lose.
• 2 lb/week — a more aggressive rate, generally only appropriate for people with significantly more weight to lose, and best done with guidance from a healthcare professional.

Faster than roughly 1% of body weight per week for an extended period is where the risk of muscle loss, nutrient deficiency, and rebound starts climbing meaningfully for most people.

Why "3,500 calories = 1 pound" is an approximation

You'll often see the rule that a pound of body fat is roughly equal to 3,500 calories, and that a 500-calorie daily deficit will therefore produce about a pound of loss per week (500 × 7 = 3,500). This is a useful planning heuristic, and it's the one used throughout this site and the CalorieToday app — but it's an approximation, not a precise law of your specific body.

In practice, the number of calories per pound of tissue lost varies with body composition, and your body's own energy expenditure adapts as you lose weight — a lighter body simply burns somewhat fewer calories at rest and during activity than a heavier one. That means a deficit that produces 1 lb/week loss in month one may produce a bit less by month three, even with identical intake, unless your target is recalculated.

This is exactly why static, one-time calculations lose accuracy over a diet — and why re-checking your numbers periodically (or letting an app do it automatically as your weight changes) matters more than getting the initial number perfect.

Signs your deficit is too aggressive

Your body will usually tell you when a deficit has gone from "challenging but sustainable" to "too much." Watch for:

• Persistent fatigue that doesn't improve with a good night's sleep, or a noticeable drop in workout performance.
• Hair loss or brittle nails, often a sign of inadequate protein or overall calorie intake over a sustained period.
• Binge-restrict cycles — swinging between very strict days and days of losing control around food, which usually signals the baseline deficit is too large to sustain psychologically.
• Mood changes, irritability, or losing your period (in people who menstruate), which can indicate the deficit is too severe for your body to tolerate long-term.
• Constant, intrusive hunger rather than normal, manageable appetite between meals.

If you notice several of these, it's usually a sign to reduce the size of the deficit — eat a bit more, aim for a slower rate of loss — rather than push through. Sustainable weight loss is a marathon, and a deficit you can't maintain isn't actually working, no matter what the math says on paper.

A practical checklist

Putting it into practice

The math above gives you a starting target, but the day-to-day work is in tracking — logging what you actually eat, weighing in consistently, and watching the trend rather than reacting to any single number. That's the gap CalorieToday is built to fill: a fast food search across a 23,000+ item database, simple weight and water logging, and charts that show your real trend so your calorie target can be adjusted as your body actually responds, not just as a formula predicts.

Start with your numbers using the free TDEE calculator, then track day to day with CalorieToday — free, private, and built around the same formulas covered in this article.