🧰 ToolPicoAll Tools →

Weight Loss Calculator

How many weeks until you reach your goal weight, and how big a daily calorie deficit does it take? Calculate BMR/TDEE, calorie deficit & timeline, BMI & ideal weight, macro split, and GLP-1 (Ozempic/Wegovy) expectations — all in one tool, in pounds, instantly and free.

Method: Mifflin-St Jeor 3,500 kcal ≈ 1 lb fat Healthy pace 1–2 lb/wk Updated: Jul 21, 2026
yrs
ft
in
lb
%
If provided, BMR switches to the more accurate Katch-McArdle formula (based on lean mass).

BMR is your basal metabolic rate (burned at rest); TDEE is total calories burned per day with activity. Eat around TDEE to maintain weight, below it to lose.

lb
1.00 lb / week
Healthy range is 0.5–2 lb/week. Gentle (0.5) preserves muscle; aggressive (2.0) is faster but harder to sustain.

Based on your goal weight and pace, this shows the daily calorie deficit needed, your daily target calories, and how many weeks until you reach your goal.

Based on your height and weight, this shows your BMI (body mass index), your category, the healthy weight range for your height, and the average of 4 classic ideal-weight formulas. Age and gender are taken from the profile above.

kcal
Don't leave this blank. Tap a chip below to auto-fill from your TDEE.

Splits your target calories into protein / carbs / fat in grams. Protein (1 g = 4 kcal) matters most for fullness and preserving muscle while losing weight; fat is 1 g = 9 kcal, carbs 1 g = 4 kcal.

lb

Based on clinical trial averages for this medication, this shows the expected weight/timeline range, dose schedule, and a realistic outlook. This is not medical advice; these medications are used only under a doctor's supervision.

Quick answer Losing 1 lb of body fat takes about a 3,500 kcal deficit. A 500-calorie daily deficit (7 × 500 = 3,500 kcal/week) is about 1 lb of loss per week — one of the most commonly recommended, sustainable paces. Enter your info above to get your own daily calorie target and timeline.
3,500 kcal≈ 1 lb body fat
1–2 lbHealthy loss per week
18.5–24.9Normal BMI range
1,200 / 1,500Min. calories (F / M)
⚕️ Not medical advice: This tool is for informational purposes only and does not replace the guidance of a doctor, registered dietitian, or other healthcare professional. Calculations are based on the Mifflin-St Jeor equation and the 3,500 kcal ≈ 1 lb assumption; actual results vary from person to person due to water balance, muscle mass, hormones, medication, and metabolic adaptation. Talk to a healthcare professional before starting a new diet, exercise, or medication program.
⚖ Weight Loss Calculator — ToolPico ↗

How does the weight loss calculator work?

A full explanation of the calorie deficit, BMR/TDEE, timeline, and healthy pace logic — with citable formulas and clear answers.

Weight loss calculation uses the gap between the calories you burn per day (TDEE) and the calories you eat — your calorie deficit — to estimate how much weight you can lose over a given time. The core scientific assumption: one pound of body fat stores about 3,500 kcal of energy. So dividing your total deficit by 3,500 gives you roughly how many pounds of fat you'll lose.

How many calories does it take to lose a pound?

Quick answerAbout 3,500 kcal. Since 1 lb of fat ≈ 3,500 kcal, losing 1 pound requires a total deficit of roughly 3,500 kcal. A 500 kcal/day deficit adds up to about 3,500 kcal/week — roughly 1 lb lost. This is an average assumption; actual loss varies, and early weeks often show a faster drop on the scale from water loss.

What are BMR and TDEE, and how are they calculated?

Quick answerBMR is the energy your body burns at complete rest. In imperial units, Mifflin-St Jeor gives BMR = 4.536×weight(lb) + 15.875×height(in) − 5×age + 5 for men, with −161 instead of +5 for women. TDEE = BMR × activity factor (1.2 sedentary → 1.9 extra active) and estimates the total calories you burn per day.

For example, a 30-year-old man who is 5'9" (69 in) and 187 lb has a BMR of roughly 4.536×187 + 15.875×69 − 5×30 + 5 ≈ 1,799 kcal. If lightly active (×1.375), his TDEE is about 2,473 kcal. Eating around 2,473 kcal maintains his weight; eating below that causes weight loss.

How many pounds a week is healthy to lose?

Quick answerGenerally, 1–2 lb per week (roughly 0.5–1% of body weight) is considered healthy and sustainable. Faster loss raises the risk of muscle loss, fatigue, gallstones, and the yo-yo effect. Daily calories generally shouldn't drop below ~1,200 kcal for women, ~1,500 kcal for men. Public health guidance considers losing up to about 5% of body weight per month reasonable.

How long will it take to reach my goal weight?

Quick answerWeeks = (current weight − goal weight) ÷ weekly pace. Losing 20 lb at a pace of 1 lb/week takes about 20 weeks (~4.5 months). Because TDEE drops somewhat as you lose weight, the realistic timeline is often a few weeks longer than this simple calculation; the tool flags this as a "realistic timeline."

What should I expect from GLP-1 medications (Ozempic / Wegovy / Mounjaro)?

GLP-1 receptor agonists help with weight loss mainly by suppressing appetite. In the STEP trials, semaglutide (Wegovy 2.4 mg) produced an average loss of about ~15% of body weight over 68 weeks; in the SURMOUNT trials, tirzepatide (Mounjaro/Zepbound) produced about ~20–22% over 72 weeks. Typical early-month loss is roughly 4–9 lb/month as the dose is titrated up. These medications are used only under a doctor's supervision alongside nutrition and exercise, and some weight may return if the medication is stopped.

Sources: Mifflin MD & St Jeor ST (1990) equation · STEP (semaglutide) and SURMOUNT (tirzepatide) phase-3 trial averages · Last updated: July 2026. These are averages, not a guarantee of individual results.

Daily calorie deficit → monthly pounds lost (quick table)

Using the 3,500 kcal ≈ 1 lb assumption, the approximate weekly and monthly (4.3 weeks) pound loss for a fixed daily deficit. Use the calculator above for your own numbers.

Daily calorie deficit → estimated loss (fat, average)
Daily deficitWeeklyMonthly (~4.3 wk)
250 kcal~0.5 lb~2.2 lb
300 kcal~0.6 lb~2.6 lb
500 kcal~1.0 lb~4.3 lb
750 kcal~1.5 lb~6.5 lb
1,000 kcal~2.0 lb~8.7 lb

Popular calculations

Reference tables & citable facts

BMI categories, activity multipliers, healthy pace thresholds, and GLP-1 clinical averages — machine- and human-readable.

World Health Organization (WHO) BMI classification (adult)
CategoryBMI range
Underweight< 18.5
Normal18.5 – 24.9
Overweight25.0 – 29.9
Obese — Class I30.0 – 34.9
Obese — Class II35.0 – 39.9
Obese — Class III (severe)≥ 40.0

Source: WHO adult BMI classification. BMI does not distinguish muscle from fat mass and can be misleading for athletes.

TDEE activity multipliers (used with Mifflin-St Jeor)
LevelDescriptionFactor
SedentaryDesk job, no exercise1.2
Lightly activeLight exercise 1–3 days/week1.375
Moderately activeExercise 3–5 days/week1.55
Very activeExercise 6–7 days/week1.725
Extra activeHard physical labor / 2x/day training1.9

TDEE = BMR × factor. Picking one level lower than you think tends to be more accurate for most people.

Weekly pace, daily deficit, and safety
PaceDaily deficitAssessment
0.5 lb/wk~250 kcalVery gentle — preserves muscle, slow
1.0 lb/wk~500 kcalRecommended — sustainable
1.5 lb/wk~750 kcalModerate-fast — track closely
2.0 lb/wk~1,000 kcalAggressive — short-term only

Minimum calories: ~1,200 kcal for women, ~1,500 kcal for men. Going lower should only be done under a doctor's or dietitian's supervision.

GLP-1 medications — average clinical trial weight loss
Medication (active ingredient)DurationAverage loss
Wegovy (semaglutide 2.4 mg)68 weeks~15%
Ozempic (semaglutide 1–2 mg)~40–68 weeks~6–10%
Mounjaro/Zepbound (tirzepatide)72 weeks~20–22%
Saxenda (liraglutide 3.0 mg)56 weeks~8%

Source: STEP (semaglutide) and SURMOUNT (tirzepatide) phase-3 trial averages. Individual results depend on dose, adherence, diet, and exercise; used only under a doctor's supervision.

Add this calculator to your site (embed code)

Embed the weight loss calculator on your own website for free. Copy the code below into your HTML — the tool runs in a simplified view and links back to this page as its source.

The embedded tool has a fixed layout; you can adjust the height value to fit your site. No ads or personal data, runs entirely client-side.

Weight loss & nutrition glossary

Short definitions of the core terms used in these calculations.

BMR (basal metabolic rate)The daily calories your body burns for basic life functions at complete rest.
TDEETotal daily energy expenditure — BMR multiplied by activity; the total calories you burn per day.
Calorie deficitEating fewer calories than you burn. The basic requirement for fat loss; 1 lb of fat ≈ 3,500 kcal.
BMI703 × weight(lb) ÷ height(in)². Classifies weight status; doesn't distinguish muscle from fat.
Ideal weight rangeThe healthy weight range for your height, corresponding to a normal BMI (18.5–24.9).
MacronutrientsProtein, carbohydrate, and fat. How calories split across these three shapes your eating plan.
Metabolic adaptationYour metabolism slowing as you lose weight, meaning a fixed deficit yields less loss over time.
GLP-1 agonistAn injectable class of appetite-suppressing medication (semaglutide, tirzepatide, liraglutide).
PlateauWeight loss stalling after a period of progress; usually requires a calorie or activity adjustment.
Yo-yo effectQuickly regaining weight lost too fast; common with overly aggressive diets.
Katch-McArdle formulaA BMR formula based on lean body mass instead of total weight; used when you enter your body fat %.

In-depth guides

Detailed answers to the most common weight loss questions.

How many pounds will a 500-calorie daily deficit lose in a month?

A 500 kcal deficit per day is 7×500 = 3,500 kcal per week. Using the 1 lb ≈ 3,500 kcal assumption, that's about 1 lb per week, or roughly 4.3 lb over a month (4.3 weeks). This is close to the widely recommended 1 lb/week pace.

You may see a faster drop on the scale in the first 1–2 weeks — most of that early loss is water and glycogen, not fat. Use the "Target & Timeline" tab above, set the pace to 1 lb/week, and see your own timeline.

Why does weight loss stall after a while? (plateau)

As you lose weight, your body gets smaller and burns fewer calories (metabolic adaptation). A diet that started with a 500 kcal deficit can stop being a deficit at all after losing several pounds — progress stalls. This is called a plateau.

The usual fix is to recalculate your calories against your current weight, increase protein and activity, or take a short "maintenance" break. That's why it's recommended to recheck your TDEE with your current weight about once a month.

What should I expect in the first month on Ozempic/Wegovy?

Because the dose is increased gradually, the first month is usually the slowest — typical loss is around 4–9 lb that month. The effect becomes more noticeable as the dose reaches its target (e.g., semaglutide 2.4 mg). Average total loss over 68 weeks is ~15% for Wegovy and ~20–22% for tirzepatide.

Important: These medications are used only with a doctor's prescription and supervision, alongside nutrition and exercise. The "GLP-1" tab shows the expected range based on your own starting weight — but this is not medical advice.

Frequently asked questions

How many calories does it take to lose a pound?
One pound of body fat stores roughly 3,500 kcal of energy. So losing 1 lb of fat requires a total deficit of about 3,500 kcal. A 500 kcal/day deficit gives about 1 lb lost per week. This is an average assumption; it varies with water balance and muscle mass.
How many pounds will a 500-calorie daily deficit lose per month?
A 500 kcal/day deficit is 3,500 kcal/week, or about 1 lb/week; over a month (~4.3 weeks) that's about ~4.3 lb. It's one of the healthiest, most sustainable paces. Early weeks may show a faster scale drop from water loss.
How many pounds a week is healthy to lose?
The general recommendation is 1–2 lb per week (about 0.5–1% of body weight). Faster loss increases the risk of muscle loss, fatigue, and the yo-yo effect. Calories generally shouldn't drop below ~1,200 kcal for women or ~1,500 kcal for men.
How are BMR and TDEE calculated?
Mifflin-St Jeor (imperial): BMR = 4.536×weight(lb) + 15.875×height(in) − 5×age + 5 for men, with −161 for women. TDEE = BMR × activity factor (1.2–1.9). BMR is burned at rest; TDEE is your total daily burn with activity.
How are BMI and ideal weight calculated?
BMI = 703 × weight(lb) ÷ height(in)²; 18.5–24.9 is considered normal. The ideal weight range is the weight corresponding to a normal BMI for your height. The tool also shows the average of the Devine, Robinson, Miller, and Hamwi formulas. BMI alone is not a diagnostic tool.
How long will it take to reach my goal weight?
Weeks = (current − goal weight) ÷ weekly pace. Losing 20 lb at 1 lb/week takes about 20 weeks (~4.5 months). Because of metabolic adaptation, the real timeline often runs a few weeks longer. The "Target & Timeline" tab calculates this for you.
How much weight can you lose on Ozempic or Wegovy?
Clinical averages: semaglutide (Wegovy 2.4 mg) about ~15% over 68 weeks; tirzepatide (Mounjaro/Zepbound) about ~20–22% over 72 weeks. Typical early-month loss is roughly 4–9 lb. Used only under a doctor's supervision alongside nutrition and exercise; results vary by person.
Does the calculator support kilograms and centimeters?
Yes. Use the Units toggle above the profile fields to switch every tab — TDEE, Target & Timeline, BMI, Macros, and GLP-1 — between imperial (lb, ft/in) and metric (kg, cm). Values you've already entered convert automatically when you switch.
What is the Katch-McArdle formula, and when is it used?
Katch-McArdle estimates BMR from lean body mass: BMR = 370 + 21.6 × lean mass (kg), where lean mass = weight × (1 − body fat %). It's often more accurate than Mifflin-St Jeor if you know your body fat percentage. Enter an optional body fat % in the profile section above and the calculator automatically switches to Katch-McArdle for BMR/TDEE.
Is this calculator medical advice?
No. ToolPico's Weight Loss Calculator is for informational purposes only and does not replace the evaluation of a doctor, dietitian, or other healthcare professional. Always consult a healthcare professional if you have a chronic condition, are pregnant, take medication, or have other special circumstances.
Where do these numbers come from, and when were they updated?
Calculations are based on the Mifflin-St Jeor (1990) equation, WHO BMI classification, and the 3,500 kcal ≈ 1 lb assumption. GLP-1 figures come from STEP and SURMOUNT phase-3 trial averages. Last updated: July 21, 2026.

Methodology & sources

ToolPico's Weight Loss Calculator is a free, independent tool. The calculation engine uses the Mifflin-St Jeor equation (imperial form) for basal metabolism, standard activity multipliers (1.2–1.9) for daily expenditure, the 3,500 kcal ≈ 1 lb assumption for calorie-to-weight conversion, and 703 × lb ÷ in² for BMI. The ideal weight range is calculated from a normal BMI (18.5–24.9) and the average of the Devine, Robinson, Miller, and Hamwi formulas.

Sources: Mifflin MD, St Jeor ST, et al. (1990) energy equation · World Health Organization (WHO) BMI classification · STEP (semaglutide) and SURMOUNT (tirzepatide) phase-3 trial averages for GLP-1 figures. Last updated: July 21, 2026. All results are for informational purposes and are not medical advice; consult a doctor or dietitian for a personal plan.

🔗 Add this tool to your site

Copy the code below into your own site. The tool is free, always up to date, and runs entirely on your page. No sign-up required.

Preview →
Explore all ToolPico tools →
⚡ Built with ToolPico · toolpico.com