Project your future weight based on today's calorie intake and activity habits.
Please enter a valid weight.
Male
Female
Sedentary (Little to no exercise)
Lightly Active (1-3 days/week)
Moderately Active (3-5 days/week)
Very Active (6-7 days/week)
Extra Active (Physical job or 2x training)
This determines your baseline calorie burn (TDEE).
Today's Habits
Total calories from all food and drink today.
Only include active exercise, not base metabolism.
Projected Weight in 90 Days
— lbs
Based on continuing today's habits.
Daily Calorie Balance
—
Est. Weekly Change
—
Weight in 1 Year
—
Weight Projection Timeline
Timeframe
Projected Weight
Total Change
1 Week
—
—
1 Month
—
—
3 Months
—
—
6 Months
—
—
1 Year
—
—
Table 1: Estimated weight milestones if daily habits remain constant.
What is an "If Everyday Was Like Today You'd Weigh" Calculator?
The If Everyday Was Like Today You'd Weigh Calculator is a specialized financial-style projection tool for your physical health. Unlike standard BMI calculators that only assess your current state, this tool acts as a predictive model. It answers a critical question: "If I repeated today's eating and exercise behaviors every single day for the next year, what would my weight become?"
Weight management is effectively a math problem involving energy balance. By treating your daily caloric intake and expenditure as a constant variable, we can project a trend line—similar to calculating compound interest on a bank account, but for your body mass.
The Science Behind the Calculation
This calculator uses the principles of thermodynamics and the Mifflin-St Jeor Equation, which is widely considered the most accurate method for estimating Basal Metabolic Rate (BMR).
The Formula Variables
Variable
Meaning
Unit
BMR
Basal Metabolic Rate (Energy burned at rest)
Calories/Day
TDEE
Total Daily Energy Expenditure (BMR × Activity)
Calories/Day
Net Balance
Calories Consumed – (TDEE + Exercise)
Calories/Day
3,500 Rule
Approximate energy in 1 lb of body fat
Calories
Table 2: Key variables used in weight projection logic.
Mathematical Steps
Calculate BMR: We determine how many calories your body needs just to exist based on your height, weight, age, and gender.
Determine TDEE: We multiply your BMR by your activity factor (1.2 to 1.9) to find your maintenance level.
Scenario: John is a 30-year-old male, 180 lbs, 5'10", sedentary. His maintenance calories are approx 2,150.
"Today's" Behavior: He went to a party and ate 3,500 calories with no exercise.
The Calculation: Surplus = 3,500 – 2,150 = +1,350 calories.
Daily Weight Gain = 1,350 / 3,500 ≈ 0.38 lbs per day.
Result: If everyday was like today, John would gain roughly 2.7 lbs per week, adding over 100 lbs in a year (theoretically).
Example 2: The Deficit Day
Scenario: Sarah is a 45-year-old female, 160 lbs, 5'4″, lightly active. Maintenance is approx 1,900.
"Today's" Behavior: She ate 1,500 calories and jogged for 300 calories.
The Calculation: Total Burn = 1,900 + 300 = 2,200.
Net Balance = 1,500 – 2,200 = -700 calories.
Daily Weight Loss = -700 / 3,500 = -0.2 lbs.
Result: If everyday was like today, Sarah would lose about 1.4 lbs per week.
How to Use This Calculator for Best Results
Be Honest with Inputs: Underestimating food or overestimating exercise is the most common error in weight projection.
Use "Typical" Days for Long-term Planning: While it's fun to see what happens if you eat pizza every day, use an average day to get a realistic long-term health forecast.
Update Regularity: As you lose weight, your BMR decreases. A 200lb person burns more than a 150lb person. Re-calculate every 10 lbs of change.
Key Factors That Affect Your Results
While the If Everyday Was Like Today You'd Weigh Calculator provides a mathematical projection, biology is complex. Consider these factors:
Metabolic Adaptation: As you lose weight, your body becomes more efficient, burning fewer calories. The calculator assumes a linear progression, but in reality, weight loss often slows down.
Water Weight Fluctuations: High sodium or carbohydrate intake "today" can cause temporary water retention, masking fat loss.
TEF (Thermic Effect of Food): Protein requires more energy to digest than fats or carbs. A high-protein diet might yield better results than the raw numbers suggest.
Non-Exercise Activity Thermogenesis (NEAT): Fidgeting, standing, and walking vary daily. If "today" was a lazy Sunday, do not project that for the whole year.
Hormonal Changes: Stress (cortisol) and sleep deprivation can impact metabolic rate and fat storage mechanisms.
Muscle Mass: If you are strength training, you might gain weight (muscle) while losing fat. The scale number might go up, but body composition improves.
Frequently Asked Questions (FAQ)
Q: Is the 3,500 calorie rule accurate?
A: It is a strong general rule of thumb. While individual variations exist, 3,500 calories roughly equates to 1 pound of stored adipose tissue (fat).
Q: Why does the calculator show I'd gain 100 lbs?
A: If you have a large surplus "today" and project it linearly for 365 days, the number will be huge. In reality, as you gain weight, your maintenance needs rise, eventually creating a new equilibrium weight.
Q: Can I target specific body parts for weight loss?
A: No. Calorie deficits cause systemic fat loss. You cannot spot-reduce belly fat just by changing today's habits.
Q: Does this account for muscle gain?
A: No. This calculator projects total body weight based on energy balance. It does not distinguish between fat mass and lean muscle mass.
Q: How accurate is the BMR calculation?
A: The Mifflin-St Jeor equation is accurate to within 10% for most people. For athletes or those with metabolic conditions, results may vary.
Q: What if I have a "cheat day"?
A: This calculator assumes everyday is exactly like today. If today is a cheat day, the projection will show weight gain. Use an average day for better accuracy.