1300 calories a day weight loss calculator shows your maintenance calories, the daily deficit created by eating 1300 calories, and how that translates into projected weekly weight loss so you can plan a safe, sustainable journey.
Calculate your 1300-calorie weight loss pace
Realistic range 40–200 kg
Used to estimate basal metabolic rate (BMR)
Metabolism generally slows with age
Male
Female
Needed for Mifflin-St Jeor equation
Sedentary (little exercise)
Lightly active (1-3 days/week)
Moderately active (3-5 days/week)
Very active (6-7 days/week)
Athlete (physical job + training)
Scales your BMR to total daily energy expenditure (TDEE)
Used to estimate timeline at a 1300 calorie plan
Projected weekly loss: 0.00 kg
8-week projection at 1300 calories per day
Week
Projected Weight (kg)
Cumulative Loss (kg)
Total Deficit (kcal)
Projected weightMaintenance weight line
What is the 1300 calories a day weight loss calculator?
The 1300 calories a day weight loss calculator estimates how eating 1300 calories compares with your personal maintenance calories so you can predict weekly weight change. It is designed for adults who need a clear view of whether 1300 calories is appropriate, borderline, or too aggressive based on their size and activity.
People who benefit include those tightening a deficit after a maintenance phase, individuals who plateaued on higher calories, and planners who need a timeline to hit a specific goal date. A common misconception is that 1300 calories automatically guarantees rapid fat loss; the calculator shows that results depend on your total daily energy expenditure, not the target alone.
1300 calories a day weight loss calculator Formula and Mathematical Explanation
This 1300 calories a day weight loss calculator uses the Mifflin-St Jeor equation to estimate basal metabolic rate (BMR), multiplies by an activity factor to get total daily energy expenditure (TDEE), then computes the calorie deficit created by eating 1300 calories. Dividing the weekly deficit by 7700 kcal (approximate energy in 1 kg of fat) yields projected weekly weight loss.
Variables used in the 1300 calories a day weight loss calculator
Variable
Meaning
Unit
Typical range
Weight
Current body mass
kg
40–200
Height
Stature for BMR
cm
140–210
Age
Metabolic adjustment
years
14–80
Activity factor
Multiplier from lifestyle
unitless
1.2–1.9
TDEE
Calories to maintain weight
kcal/day
1500–3500
Daily deficit
TDEE minus 1300
kcal/day
0–1800
Weekly loss
Projected fat loss
kg/week
0–1.6
Timeline
Days to goal
days
10–240
Practical Examples (Real-World Use Cases)
Example 1: A 70 kg, 170 cm, 30-year-old woman, lightly active (1.375). BMR ≈ 10×70 + 6.25×170 – 5×30 – 161 = 1426 kcal. TDEE ≈ 1426 × 1.375 = 1962 kcal. Eating 1300 calories creates a 662 kcal daily deficit. Weekly loss ≈ 662×7/7700 = 0.60 kg. A 5 kg target would take about 58 days.
Example 2: An 85 kg, 180 cm, 40-year-old man, moderately active (1.55). BMR ≈ 10×85 + 6.25×180 – 5×40 + 5 = 1795 kcal. TDEE ≈ 1795 × 1.55 = 2782 kcal. Deficit ≈ 1482 kcal/day. Weekly loss ≈ 1.35 kg. A 6 kg target would take roughly 34 days, but this deficit may be too aggressive, so adding planned refeeds could be safer.
How to Use This 1300 calories a day weight loss calculator
Enter your weight, height, age, sex, activity level, and goal loss. The 1300 calories a day weight loss calculator instantly shows maintenance calories, your deficit at 1300 calories, and projected weekly weight loss.
Read the primary result to see the expected weekly change. Review intermediate values to confirm TDEE and whether the deficit is realistic. If the timeline seems too short or the deficit is above 1000 kcal/day, consider increasing calories or activity for sustainability.
Key Factors That Affect 1300 calories a day weight loss calculator Results
Multiple levers influence the 1300 calories a day weight loss calculator outputs:
Metabolic rate: Higher lean mass raises BMR, shrinking the deficit at 1300 calories.
Activity level: More movement widens the gap between TDEE and 1300, speeding loss.
Diet adherence: Missed logging or hidden calories erase the predicted deficit.
Adaptive thermogenesis: Prolonged deficits can reduce TDEE, slowing loss over time.
Macronutrient balance: Adequate protein preserves muscle, keeping BMR steadier.
Hydration and glycogen: Early rapid drops often reflect water, not fat; use weekly averages.
Sleep and stress: Poor recovery elevates cortisol, sometimes increasing water retention.
Medical factors: Hormonal shifts or medications can change energy needs; consult a professional.
Frequently Asked Questions (FAQ)
Is 1300 calories safe for everyone? No, smaller people may need it, but larger or very active individuals may require more to avoid excessive deficits.
How fast will I lose weight at 1300 calories? The 1300 calories a day weight loss calculator estimates weekly loss based on your TDEE; typical ranges are 0.3–1.3 kg/week.
What if my daily deficit is under 300 kcal? Results will be slow; consider adding activity or modestly lowering calories.
Do I need to eat back exercise calories? If your activity exceeds the selected factor, you may need to add calories to keep the deficit moderate.
Can I use this during a reverse diet? Yes, track how close 1300 calories is to maintenance to decide how to step up.
How accurate is the BMR formula? Mifflin-St Jeor is an estimate; body composition and genetics create variance.
Why did my weight stall? Water retention, menstrual cycle, or logging errors can mask true fat loss for several days.
Is 7700 kcal per kg exact? It is an approximation; fat-free mass changes and hormonal shifts affect the true energy cost.
var defaultValues = {
weightKg:70,
heightCm:170,
age:30,
gender:"female",
activity:"1.375″,
targetLossKg:5
};
function resetForm(){
document.getElementById("weightKg").value=defaultValues.weightKg;
document.getElementById("heightCm").value=defaultValues.heightCm;
document.getElementById("age").value=defaultValues.age;
document.getElementById("gender").value=defaultValues.gender;
document.getElementById("activity").value=defaultValues.activity;
document.getElementById("targetLossKg").value=defaultValues.targetLossKg;
clearErrors();
calculateAll();
}
function clearErrors(){
document.getElementById("error-weightKg").innerHTML="";
document.getElementById("error-heightCm").innerHTML="";
document.getElementById("error-age").innerHTML="";
document.getElementById("error-gender").innerHTML="";
document.getElementById("error-activity").innerHTML="";
document.getElementById("error-targetLossKg").innerHTML="";
}
function validateInputs(values){
var valid=true;
clearErrors();
if(isNaN(values.weightKg)||values.weightKg<=0){document.getElementById("error-weightKg").innerHTML="Enter a valid weight above 0.";valid=false;}
if(isNaN(values.heightCm)||values.heightCm<=0){document.getElementById("error-heightCm").innerHTML="Enter a valid height above 0.";valid=false;}
if(isNaN(values.age)||values.age<14){document.getElementById("error-age").innerHTML="Age must be 14 or above.";valid=false;}
if(!values.gender){document.getElementById("error-gender").innerHTML="Select sex.";valid=false;}
if(isNaN(values.activity)||values.activity<1.1){document.getElementById("error-activity").innerHTML="Select activity level.";valid=false;}
if(isNaN(values.targetLossKg)||values.targetLossKg<=0){document.getElementById("error-targetLossKg").innerHTML="Goal loss must be positive.";valid=false;}
return valid;
}
function calculateAll(){
var inputs={
weightKg:parseFloat(document.getElementById("weightKg").value),
heightCm:parseFloat(document.getElementById("heightCm").value),
age:parseFloat(document.getElementById("age").value),
gender:document.getElementById("gender").value,
activity:parseFloat(document.getElementById("activity").value),
targetLossKg:parseFloat(document.getElementById("targetLossKg").value)
};
if(!validateInputs(inputs)){return;}
var bmr=0;
if(inputs.gender==="male"){bmr=10*inputs.weightKg+6.25*inputs.heightCm-5*inputs.age+5;}
else{bmr=10*inputs.weightKg+6.25*inputs.heightCm-5*inputs.age-161;}
var tdee=bmr*inputs.activity;
var dailyCalories=1300;
var dailyDeficit=tdee-dailyCalories;
if(dailyDeficit<0){dailyDeficit=0;}
var weeklyLossKg=dailyDeficit*7/7700;
var timelineDays=inputs.targetLossKg0?dailyDeficit:1);
var proteinMin=1.6*inputs.weightKg;
document.getElementById("primaryResult").innerHTML="Projected weekly loss: "+weeklyLossKg.toFixed(2)+" kg";
var summary="Maintenance (TDEE): "+Math.round(tdee)+" kcal/day. Eating 1300 kcal creates a "+Math.round(dailyDeficit)+" kcal daily deficit, leading to about "+weeklyLossKg.toFixed(2)+" kg loss per week.";
document.getElementById("summaryText").innerHTML=summary;
var list="
Total daily energy expenditure: "+Math.round(tdee)+" kcal/day
";
list+="
Daily deficit at 1300 kcal: "+Math.round(dailyDeficit)+" kcal/day
";
list+="
Protein floor: "+proteinMin.toFixed(1)+" g/day to support lean mass
";
list+="
Estimated days to lose "+inputs.targetLossKg.toFixed(1)+" kg: "+(dailyDeficit>0?Math.ceil(timelineDays):"Not achievable at surplus")+"
";
document.getElementById("intermediateList").innerHTML=list;
document.getElementById("formulaNote").innerHTML="Formula: Mifflin-St Jeor for BMR, multiplied by activity for TDEE. Weekly loss uses (TDEE – 1300) × 7 ÷ 7700.";
updateTable(inputs.weightKg,weeklyLossKg,dailyDeficit);
drawChart(inputs.weightKg,weeklyLossKg);
}
function updateTable(startWeight,weeklyLossKg,dailyDeficit){
var tbody=document.querySelector("#projectionTable tbody");
tbody.innerHTML="";
var cumulative=0;
var weeks=8;
for(var i=1;i<=weeks;i++){
cumulative+=weeklyLossKg;
var projectedWeight=startWeight-weeklyLossKg*i;
if(projectedWeight<0){projectedWeight=0;}
var totalDeficit=Math.max(dailyDeficit,0)*7*i;
var tr=document.createElement("tr");
var cells=[i,projectedWeight.toFixed(2),cumulative.toFixed(2),Math.round(totalDeficit)];
for(var j=0;j<cells.length;j++){
var td=document.createElement("td");
td.innerHTML=cells[j];
tr.appendChild(td);
}
tbody.appendChild(tr);
}
}
function drawChart(startWeight,weeklyLossKg){
var canvas=document.getElementById("projectionChart");
var ctx=canvas.getContext("2d");
ctx.clearRect(0,0,canvas.width,canvas.height);
var padding=40;
var weeks=8;
var data1=[];
var data2=[];
for(var i=0;i<=weeks;i++){
data1.push(startWeight-weeklyLossKg*i);
data2.push(startWeight);
}
var maxWeight=startWeight;
var minWeight=startWeight-weeklyLossKg*weeks;
if(minWeight<0){minWeight=0;}
var yMax=maxWeight+2;
var yMin=Math.max(minWeight-2,0);
function getX(i){return padding+(canvas.width-2*padding)*(i/weeks);}
function getY(val){return canvas.height-padding-((val-yMin)/(yMax-yMin))*(canvas.height-2*padding);}
ctx.strokeStyle="#dbe3ec";
ctx.lineWidth=1;
for(var y=0;y<=5;y++){
var value=yMin+(yMax-yMin)*y/5;
var yPos=getY(value);
ctx.beginPath();
ctx.moveTo(padding,yPos);
ctx.lineTo(canvas.width-padding,yPos);
ctx.stroke();
ctx.fillStyle="#637285";
ctx.fillText(value.toFixed(1),8,yPos+4);
}
ctx.beginPath();
ctx.strokeStyle="#004a99";
ctx.lineWidth=3;
for(var k=0;k<data1.length;k++){
var x=getX(k);
var y=getY(data1[k]);
if(k===0){ctx.moveTo(x,y);}else{ctx.lineTo(x,y);}
}
ctx.stroke();
ctx.beginPath();
ctx.strokeStyle="#28a745";
ctx.lineWidth=2;
for(var m=0;m<data2.length;m++){
var x2=getX(m);
var y2=getY(data2[m]);
if(m===0){ctx.moveTo(x2,y2);}else{ctx.lineTo(x2,y2);}
}
ctx.stroke();
ctx.fillStyle="#0f2135";
ctx.fillText("Weeks",canvas.width/2-10,canvas.height-10);
ctx.save();
ctx.translate(12,canvas.height/2+30);
ctx.rotate(-Math.PI/2);
ctx.fillText("Weight (kg)",0,0);
ctx.restore();
}
function copyResults(){
var primary=document.getElementById("primaryResult").innerText;
var summary=document.getElementById("summaryText").innerText;
var list=document.getElementById("intermediateList").innerText;
var note=document.getElementById("formulaNote").innerText;
var text=primary+"\n"+summary+"\n"+list+"\n"+note;
var temp=document.createElement("textarea");
temp.value=text;
document.body.appendChild(temp);
temp.select();
document.execCommand("copy");
document.body.removeChild(temp);
}
calculateAll();