Use this calculator for weight loss to estimate calorie deficits, expected weekly fat loss, and the number of weeks to reach your goal weight with dynamic tables and charts.
Weight Loss Inputs
Your present body weight in kilograms.
Target weight you want to reach.
Used to estimate your basal metabolic rate.
Metabolism decreases slightly with age.
Male
Female
Required for Mifflin-St Jeor BMR calculation.
Sedentary (little exercise)
Lightly active (1-3 days/week)
Moderately active (3-5 days/week)
Very active (6-7 days/week)
Athlete level
Multiplier used to estimate total daily energy expenditure.
Average calories you plan to eat per day.
Estimated weeks to goal: —
Basal Metabolic Rate (BMR): — kcal/day
Total Daily Energy Expenditure (TDEE): — kcal/day
Daily Calorie Deficit: — kcal
Projected Weekly Loss: — kg
Projected 4-Week Loss: — kg
Formula: —
Projected WeightGoal Weight
Projected Weight Change Table
Week
Projected Weight (kg)
Goal Weight (kg)
Cumulative Loss (kg)
What is calculator for weight loss?
The calculator for weight loss is a focused planning tool that estimates your basal metabolic rate, total daily energy expenditure, calorie deficit, and the weeks required to reach a goal weight. People who want structured fat loss, athletes making weight, and anyone aiming to avoid guesswork use this calculator for weight loss for clarity.
A common misconception is that a calculator for weight loss gives a guaranteed date; in reality it provides evidence-based projections that assume consistent nutrition, activity, and adherence. Another misconception is that the calculator for weight loss ignores muscle gain—its focus is fat-loss pacing, so strength training and protein intake still matter.
calculator for weight loss Formula and Mathematical Explanation
The calculator for weight loss starts with the Mifflin-St Jeor equation for BMR, multiplies it by an activity factor to find TDEE, then subtracts intended calorie intake to find daily deficit. Fat loss projection assumes roughly 7,700 kcal per kilogram of fat.
Variable Definitions for calculator for weight loss
Variable
Meaning
Unit
Typical range
Weight
Current body mass
kg
45–180
Goal weight
Target mass
kg
40–150
Height
Body stature
cm
145–200
Age
Years lived
years
18–75
Activity factor
Movement multiplier
unitless
1.2–1.9
Calorie intake
Daily energy eaten
kcal
1200–3200
Daily deficit
Calories under TDEE
kcal
200–1200
Weekly loss
Expected fat reduction
kg
0.2–1.2
Practical Examples (Real-World Use Cases)
Example 1: A 82 kg male at 175 cm, age 35, moderately active, eating 2100 kcal uses the calculator for weight loss. BMR ≈ 1757 kcal, TDEE ≈ 2723 kcal. Daily deficit ≈ 623 kcal, weekly loss ≈ 0.57 kg. To drop to 72 kg, about 17–18 weeks are projected, showing how the calculator for weight loss guides pacing.
Example 2: A 68 kg female at 165 cm, age 30, lightly active, eating 1700 kcal uses the calculator for weight loss. BMR ≈ 1428 kcal, TDEE ≈ 1964 kcal. Daily deficit ≈ 264 kcal, weekly loss ≈ 0.24 kg. To reach 62 kg, the calculator for weight loss projects roughly 25 weeks, illustrating how smaller deficits lengthen timelines.
How to Use This calculator for weight loss Calculator
Enter current weight, goal weight, height, age, sex, activity level, and planned daily calories.
Watch the calculator for weight loss update BMR, TDEE, deficit, weekly loss, and weeks to goal in real time.
Use the chart to visualize weekly projections and the table to track cumulative loss.
Adjust calories or activity and observe how the calculator for weight loss changes your timeline.
Copy results to share with a coach or log in a progress journal.
Read results by focusing on the main highlighted weeks-to-goal output; if the calculator for weight loss shows a very long timeline, increase activity or modestly lower calories while staying healthy.
Key Factors That Affect calculator for weight loss Results
1) Calorie accuracy: Miscounted portions reduce the calculator for weight loss precision. 2) Activity variability: Steps and workouts change TDEE; inconsistent movement skews projections. 3) Metabolic adaptation: Prolonged deficits can lower BMR; the calculator for weight loss assumes stable metabolism. 4) Protein intake: Adequate protein preserves lean mass, making the calculator for weight loss closer to pure fat-loss pacing. 5) Sleep and stress: Hormonal shifts can affect water weight and appetite, altering short-term readings from the calculator for weight loss. 6) Weight training: Muscle gain can mask fat loss; the calculator for weight loss focuses on fat mass trends rather than scale-only readings. 7) Hydration shifts: Water retention can temporarily hide progress the calculator for weight loss projects. 8) Hormonal cycles: Fluctuations can change scale readings even when the calculator for weight loss math is correct.
Frequently Asked Questions (FAQ)
Does the calculator for weight loss guarantee exact dates? No, it provides estimates based on your inputs.
What if my daily deficit is negative? Increase activity or reduce intake so the calculator for weight loss shows a positive deficit.
Is losing more than 1 kg per week safe? The calculator for weight loss warns when projected loss exceeds typical healthy ranges; consult a clinician.
Can I use the calculator for weight loss for muscle gain? It is optimized for fat loss projections; surplus planning differs.
How often should I update inputs? Weekly updates keep the calculator for weight loss aligned with real changes.
Does water weight affect results? Short-term shifts occur, but the calculator for weight loss emphasizes trends.
Can I set an aggressive goal? Yes, but the calculator for weight loss will show if the deficit required is unrealistic.
What activity factor should I choose? Pick the level matching your average week so the calculator for weight loss remains accurate.
Related Tools and Internal Resources
{related_keywords} – Complementary guidance to the calculator for weight loss.
{related_keywords} – Tracking aid that pairs with this calculator for weight loss.
{related_keywords} – Meal planning aligned with the calculator for weight loss.
{related_keywords} – Workout templates to reinforce the calculator for weight loss projections.
{related_keywords} – Macros breakdown tuned to the calculator for weight loss.
{related_keywords} – Hydration planner synced with the calculator for weight loss expectations.
var chartCanvas = document.getElementById('lossChart');
var chartCtx = chartCanvas.getContext('2d');
var chartData = {weeks:[], projected:[], goal:[]};
function validateInputs() {
var valid = true;
valid = checkField('currentWeight', 30, 300);
valid = checkField('goalWeight', 30, 300) && valid;
valid = checkField('height', 120, 230) && valid;
valid = checkField('age', 15, 90) && valid;
valid = checkField('calories', 800, 5000) && valid;
var activityVal = document.getElementById('activity').value;
if (isNaN(parseFloat(activityVal)) || parseFloat(activityVal) = cw) {
document.getElementById('error-goalWeight').textContent = 'Goal weight must be less than current weight.';
valid = false;
}
return valid;
}
function checkField(id, min, max) {
var val = parseFloat(document.getElementById(id).value);
var errorEl = document.getElementById('error-' + id);
if (isNaN(val)) {
errorEl.textContent = 'Enter a number.';
return false;
}
if (val <= 0) {
errorEl.textContent = 'Value must be positive.';
return false;
}
if (val max) {
errorEl.textContent = 'Value should be between ' + min + ' and ' + max + '.';
return false;
}
errorEl.textContent = ";
return true;
}
function calculateAll() {
if (!validateInputs()) {
clearResults();
return;
}
var cw = parseFloat(document.getElementById('currentWeight').value);
var gw = parseFloat(document.getElementById('goalWeight').value);
var height = parseFloat(document.getElementById('height').value);
var age = parseFloat(document.getElementById('age').value);
var sex = document.getElementById('sex').value;
var activity = parseFloat(document.getElementById('activity').value);
var calories = parseFloat(document.getElementById('calories').value);
var bmr = 0;
if (sex === 'male') {
bmr = 10 * cw + 6.25 * height – 5 * age + 5;
} else {
bmr = 10 * cw + 6.25 * height – 5 * age – 161;
}
var tdee = bmr * activity;
var deficit = tdee – calories;
var weeklyLoss = deficit > 0 ? (deficit * 7) / 7700 : 0;
var weeksToGoal = weeklyLoss > 0 ? (cw – gw) / weeklyLoss : 0;
var monthlyLoss = weeklyLoss * 4;
updateResults(bmr, tdee, deficit, weeklyLoss, monthlyLoss, weeksToGoal, cw, gw);
updateTableAndChart(cw, gw, weeklyLoss);
updateFormulaText(bmr, tdee, deficit);
}
function clearResults() {
document.getElementById('mainResult').textContent = 'Estimated weeks to goal: –';
document.getElementById('resultBMR').textContent = 'Basal Metabolic Rate (BMR): — kcal/day';
document.getElementById('resultTDEE').textContent = 'Total Daily Energy Expenditure (TDEE): — kcal/day';
document.getElementById('resultDeficit').textContent = 'Daily Calorie Deficit: — kcal';
document.getElementById('resultWeeklyLoss').textContent = 'Projected Weekly Loss: — kg';
document.getElementById('resultMonthlyLoss').textContent = 'Projected 4-Week Loss: — kg';
document.getElementById('formulaText').textContent = 'Formula: –';
document.getElementById('projectionTable').innerHTML = ";
chartCtx.clearRect(0,0,chartCanvas.width,chartCanvas.height);
}
function updateResults(bmr, tdee, deficit, weeklyLoss, monthlyLoss, weeksToGoal, cw, gw) {
document.getElementById('mainResult').textContent = 'Estimated weeks to goal: ' + (weeksToGoal > 0 ? weeksToGoal.toFixed(1) : 'N/A');
document.getElementById('resultBMR').textContent = 'Basal Metabolic Rate (BMR): ' + bmr.toFixed(0) + ' kcal/day';
document.getElementById('resultTDEE').textContent = 'Total Daily Energy Expenditure (TDEE): ' + tdee.toFixed(0) + ' kcal/day';
document.getElementById('resultDeficit').textContent = 'Daily Calorie Deficit: ' + deficit.toFixed(0) + ' kcal';
document.getElementById('resultWeeklyLoss').textContent = 'Projected Weekly Loss: ' + weeklyLoss.toFixed(2) + ' kg';
document.getElementById('resultMonthlyLoss').textContent = 'Projected 4-Week Loss: ' + monthlyLoss.toFixed(2) + ' kg';
if (deficit <= 0 || weeklyLoss <= 0) {
document.getElementById('mainResult').textContent = 'Estimated weeks to goal: increase deficit to lose weight';
}
var formulaSummary = 'Using Mifflin-St Jeor: BMR=' + bmr.toFixed(0) + ', TDEE=' + tdee.toFixed(0) + ', Deficit=' + deficit.toFixed(0) + ', Weekly loss=(Deficit×7)/7700.';
document.getElementById('formulaText').textContent = 'Formula: ' + formulaSummary;
}
function updateTableAndChart(cw, gw, weeklyLoss) {
var tbody = document.getElementById('projectionTable');
tbody.innerHTML = '';
chartData.weeks = [];
chartData.projected = [];
chartData.goal = [];
var maxWeeks = 12;
var current = cw;
var cumulativeLoss = 0;
for (var i = 1; i <= maxWeeks; i++) {
var lossThisWeek = weeklyLoss;
current = current – lossThisWeek;
if (current < gw) {
current = gw;
}
cumulativeLoss = cw – current;
var tr = document.createElement('tr');
var cells = [
i,
current.toFixed(2) + ' kg',
gw.toFixed(2) + ' kg',
cumulativeLoss.toFixed(2) + ' kg'
];
for (var j = 0; j < cells.length; j++) {
var td = document.createElement('td');
td.textContent = cells[j];
tr.appendChild(td);
}
tbody.appendChild(tr);
chartData.weeks.push(i);
chartData.projected.push(current);
chartData.goal.push(gw);
if (current <= gw) {
break;
}
}
drawChart();
}
function drawChart() {
chartCtx.clearRect(0,0,chartCanvas.width,chartCanvas.height);
var padding = 40;
var w = chartCanvas.width – padding * 2;
var h = chartCanvas.height – padding * 2;
var maxWeight = Math.max.apply(null, chartData.projected.concat(chartData.goal));
var minWeight = Math.min.apply(null, chartData.projected.concat(chartData.goal));
if (maxWeight === minWeight) {
maxWeight += 1;
minWeight -= 1;
}
chartCtx.strokeStyle = '#c8d8f3';
chartCtx.lineWidth = 1;
chartCtx.beginPath();
chartCtx.moveTo(padding, padding);
chartCtx.lineTo(padding, padding + h);
chartCtx.lineTo(padding + w, padding + h);
chartCtx.stroke();
plotLine(chartData.projected, '#004a99', w, h, padding, minWeight, maxWeight);
plotLine(chartData.goal, '#28a745', w, h, padding, minWeight, maxWeight);
}
function plotLine(arr, color, w, h, padding, minWeight, maxWeight) {
if (arr.length === 0) return;
chartCtx.beginPath();
for (var i = 0; i < arr.length; i++) {
var x = padding + (w / Math.max(arr.length – 1, 1)) * i;
var norm = (arr[i] – minWeight) / (maxWeight – minWeight);
var y = padding + h – norm * h;
if (i === 0) {
chartCtx.moveTo(x, y);
} else {
chartCtx.lineTo(x, y);
}
}
chartCtx.strokeStyle = color;
chartCtx.lineWidth = 3;
chartCtx.stroke();
}
function resetForm() {
document.getElementById('currentWeight').value = 82;
document.getElementById('goalWeight').value = 72;
document.getElementById('height').value = 175;
document.getElementById('age').value = 35;
document.getElementById('sex').value = 'male';
document.getElementById('activity').value = '1.55';
document.getElementById('calories').value = 2100;
document.getElementById('error-currentWeight').textContent = '';
document.getElementById('error-goalWeight').textContent = '';
document.getElementById('error-height').textContent = '';
document.getElementById('error-age').textContent = '';
document.getElementById('error-sex').textContent = '';
document.getElementById('error-activity').textContent = '';
document.getElementById('error-calories').textContent = '';
calculateAll();
}
function copyResults() {
var text = '';
text += document.getElementById('mainResult').textContent + '\n';
text += document.getElementById('resultBMR').textContent + '\n';
text += document.getElementById('resultTDEE').textContent + '\n';
text += document.getElementById('resultDeficit').textContent + '\n';
text += document.getElementById('resultWeeklyLoss').textContent + '\n';
text += document.getElementById('resultMonthlyLoss').textContent + '\n';
text += document.getElementById('formulaText').textContent + '\n';
if (navigator.clipboard && navigator.clipboard.writeText) {
navigator.clipboard.writeText(text);
} else {
var temp = document.createElement('textarea');
temp.value = text;
document.body.appendChild(temp);
temp.select();
try { document.execCommand('copy'); } catch(e){}
document.body.removeChild(temp);
}
}
calculateAll();