Weight Loss Calculator

Say you are a 35-year-old woman, 5'6", weighing 180 lb and lightly active, who wants to reach 150 lb. Your maintenance (TDEE) works out to roughly 2,100 calories per day. To lose 1 pound per week you subtract about a 500-calorie daily deficit, giving a target near 1,600 calories per day. You need to lose 30 lb, so at 1 lb/week that is about 30 weeks - landing you at your goal roughly seven months out, with the halfway mark (165 lb) around week 15. This weight loss calculator does that math instantly and lays out the milestone dates so the goal feels concrete instead of abstract.

The formula behind the numbers

Two pieces of math drive the result. First, maintenance calories use the Mifflin-St Jeor equation (BMR × activity factor) - the same engine behind our TDEE Calculator. Second, the deficit comes from the long-standing rule that one pound of body fat stores about 3,500 calories:

So a 1 lb/week goal means a 500 kcal/day deficit, and 2 lb/week means 1,000 kcal/day. Time to goal is simply the weight you want to lose divided by your weekly rate. The tool also enforces a safe floor and will not recommend eating below about 1,200 kcal/day (women) or 1,500 kcal/day (men).

How fast should you lose weight?

For most adults, a gradual loss of about 1 to 2 pounds per week (roughly 0.5-1 kg) is considered a sustainable, healthy pace. Slow and steady wins here: people who lose weight gradually are more likely to keep it off than those who crash diet. Faster drops in the first week or two are usually water weight, not fat. If your deficit is large enough that the calculator pins you at the minimum-calorie floor, that is a signal to choose a slower rate or extend your timeline.

Why progress slows (and what to do)

The 3,500-calorie rule is a useful planning approximation, but your body is not a spreadsheet. As you lose weight your BMR falls (a lighter body burns fewer calories), so the same intake produces a smaller deficit over time - a process called metabolic adaptation. To keep progress steady you may need to recalculate your TDEE every 10-15 lb, prioritize protein and resistance training to protect muscle, and weigh trends over several weeks rather than reacting to daily swings from food, water and sodium.

How to break through a plateau

Almost everyone hits a stall where the scale refuses to move for two or three weeks despite eating "the same." Before assuming your metabolism is broken, work through the usual culprits in order. First, confirm the stall is real by judging a 14-day weight average rather than a single morning reading - water retention from a salty meal, a hard workout, or a poor night's sleep can mask several days of genuine fat loss. Second, audit your intake honestly: portions creep upward over time, "bites and licks" while cooking add up, and weekends often undo a tidy weekday deficit. Re-weighing your food for a week usually reveals the gap. Third, recalculate. A body that is 15 lb lighter genuinely needs fewer calories, so the target that worked at the start is now too generous - re-run this weight loss calculator with your current weight to reset the number. Only after those three checks should you trim further, and then by a modest 100-200 kcal rather than slashing intake, which tends to spike hunger and backfire. Adding daily steps or a couple of strength sessions can widen the deficit without touching food at all.

Weight loss timelines at a glance

It helps to see how the weekly rate translates into real calendar time before you commit. The figures below assume a steady pace at the rate shown; in practice early weeks run a little faster (water) and later weeks a little slower (adaptation), so treat them as planning anchors:

• Lose 10 lb: about 20 weeks at 0.5 lb/week, 10 weeks at 1 lb/week, or 5 weeks at 2 lb/week.
• Lose 20 lb: about 40 weeks at 0.5 lb/week, 20 weeks at 1 lb/week, or 10 weeks at 2 lb/week.
• Lose 30 lb: about 30 weeks at 1 lb/week or 15 weeks at 2 lb/week - roughly seven versus four months.
• Lose 50 lb: about 50 weeks at 1 lb/week or 25 weeks at 2 lb/week, though larger goals almost always need a mid-course recalculation.

Notice that doubling the rate halves the time but also doubles the daily deficit, which shrinks how much you get to eat. Many people find a 1 lb/week pace the sweet spot: visible monthly progress with a calorie target that still leaves room for a normal social life. If you are aiming at a fixed date - a wedding or a reunion - work backward from the date to see whether the required rate is realistic or whether the goal needs to shift.

Make the deficit sustainable

• Anchor on protein: roughly 0.7-1 g per pound of body weight helps preserve muscle and curbs hunger - the Protein Calculator and Macro Calculator turn that into daily grams.
• Move more, NEAT included: everyday activity (walking, chores) often burns more than formal workouts.
• Pick a rate you can keep: a smaller deficit you actually maintain beats an aggressive one you abandon.
• Track, then adjust: if the scale stalls for 2-3 weeks at a true deficit, recalculate and trim 100-200 kcal.

How to use this weight loss calculator

You only need a few honest numbers to get a realistic plan. Work through the fields in order:

1. Units: choose imperial (lb, ft-in) or metric (kg, cm). All later fields follow your choice.
2. Age and sex: both feed the Mifflin-St Jeor BMR equation, so a 30-year-old man and a 50-year-old woman of the same weight get different targets.
3. Height and current weight: enter today's numbers. Re-weigh and update these every few weeks as you progress.
4. Activity level: pick the option that matches a typical week, not your best day. Most people overestimate this, which inflates the calorie target.
5. Goal weight: enter a realistic target below your current weight. The tool needs a number lower than where you are now to draw a timeline.
6. Weekly rate: select how fast you want to lose, usually 0.5 to 2 lb per week. A gentler rate gives a higher, easier-to-live-with calorie target.

The result updates instantly. Read the daily calorie target first, then the weeks to goal and the projected goal date, and finally the milestone dates that mark each quarter of the journey.

A second worked example: a faster 2 lb/week plan

Take a 40-year-old man, 5'10", weighing 220 lb and moderately active, aiming for 190 lb. His maintenance (TDEE) is roughly 3,000 calories per day. Choosing the more aggressive 2 lb/week rate means a 1,000-calorie daily deficit, putting his target near 2,000 calories per day - still comfortably above the safe floor for men. He wants to lose 30 lb, so at 2 lb/week the timeline is about 15 weeks, with the halfway point (205 lb) near week 8. Compared with the 1 lb/week woman in the first example, he reaches a similar 30 lb loss in half the time, but he has far less day-to-day eating room and will likely feel hungrier - a trade-off the calculator makes visible before he commits.

Who this calculator is for

This tool is built for healthy adults who want to turn a vague goal into a concrete plan with dates. It fits:

• Anyone starting out who needs a daily calorie target and a realistic finish date instead of guessing.
• People comparing rates who want to see how 0.5 vs. 1 vs. 2 lb per week changes both the target and the timeline.
• Event planners working backward from a wedding, holiday, or race to check whether a goal is achievable in the time available.
• Returning losers who hit a plateau and need to recalculate around a new, lower body weight.

It is not intended for children or teenagers, pregnant or breastfeeding women, or people managing a medical condition or eating disorder - those situations need professional guidance.

Key terms explained

• BMR (basal metabolic rate): the calories your body burns at complete rest just to keep you alive.
• TDEE (total daily energy expenditure): your BMR multiplied by an activity factor - the intake that keeps your weight stable.
• Calorie deficit: eating fewer calories than your TDEE, the condition required to lose body weight.
• Mifflin-St Jeor equation: a widely used formula that estimates BMR from your weight, height, age, and sex.
• NEAT (non-exercise activity thermogenesis): the calories you burn through daily movement that is not formal exercise - walking, fidgeting, chores.
• Metabolic adaptation: the gradual drop in calorie burn as you get lighter, which is why a deficit shrinks over time.

What changes the result the most

If you adjust the inputs and watch the target move, a few factors clearly dominate:

• Body size: a larger, heavier body has a higher BMR and TDEE, so the same deficit allows more food.
• Activity level: stepping from sedentary to moderately active can add several hundred calories to your maintenance number.
• Chosen weekly rate: doubling the rate from 1 to 2 lb/week doubles the deficit and halves the timeline, but cuts your daily allowance sharply.
• Sex and age: men generally have higher BMR than women of the same size, and BMR drifts down with age.
• The safe-minimum floor: if your math falls below the floor, the tool caps the target there, which stretches the timeline beyond the rate you picked.

Limitations and assumptions

Treat the output as a planning estimate, not a guarantee. Keep these assumptions in mind:

• It uses population-average formulas (Mifflin-St Jeor and the 3,500 kcal-per-pound rule); your true metabolism can differ by a few hundred calories.
• It assumes linear weight loss, but real progress is bumpy and slows as you adapt.
• It models total body weight, not the split between fat, muscle, and water.
• It does not account for medications, hormones, sleep, stress, or medical conditions that affect weight.
• It assumes you can accurately hit the calorie target; under-reporting intake is common and a frequent reason progress lags the prediction.

How it compares to related calculators

This page answers "how long will it take and what should I eat to reach my goal weight?" If you have a different question, a sister tool fits better:

• To find the exact deficit for a target rate, use the Calorie Deficit Calculator.
• To estimate maintenance calories on their own, use the TDEE Calculator.
• For a general daily calorie need (loss, maintenance, or gain), use the Calorie Calculator.
• To isolate just your resting burn, use the BMR Calculator.
• To turn your calorie target into protein, carb and fat grams, use the Macro Calculator.
• To check where your weight sits relative to height, use the BMI Calculator; to set the goal itself, see the Ideal Weight Calculator.

Sources

• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) - Weight Management.
• Centers for Disease Control and Prevention (CDC) - Losing Weight (about 1-2 lb per week).
• National Heart, Lung, and Blood Institute (NHLBI) - Aim for a Healthy Weight.
• Mifflin MD, St Jeor ST, et al. (1990), American Journal of Clinical Nutrition - the Mifflin-St Jeor BMR equation.

This calculator is an educational estimate and is not medical advice. Consult a doctor or registered dietitian before changing your diet.