Example 1
- Deficit: 500 kcal/day
- Weeks: 4
-1.82 kg
500 kcal for 4 weeks gives about -1.82 kg.
Weekly weight change calculator
Type a daily deficit and a week count. The calculator multiplies them by 7 and divides by 7700. Five hundred kcal for 4 weeks is about -1.82 kg. Surplus and a meal plan are not built here.
Δkg = (-deficit × 7 × weeks) / 7700. Daily deficit lives on the calorie deficit calculator. Gain from a surplus is on the weight gain calculator.
Result
Daily deficit (kcal) and Number of weeks. Mass-change sketch shows up here.
How it works
The formula is short: daily deficit times seven times the week count, then divide by 7700 and put a minus on it, because this is a loss. Five hundred kcal for 4 weeks is 500 × 28 = 14000, and 14000 / 7700 is about 1.82, so the result is -1.82 kg. One week at the same 500 kcal is about -0.45 kg. A thousand kcal for one week is 7000 / 7700, about -0.91 kg, still less than a kilogram on the nose.
People type “weight gain calculator” and land on surplus: TDEE plus extra calories. You do not add a surplus here. The field wants a positive deficit. A negative number in that field is not a bulk trick. Gain from a surplus lives on the neighboring card. TDEE and Mifflin are not inputs. You compute the day next door, then paste the difference here.
Three hundred kcal for 8 weeks is about -2.18 kg. Three hundred fifty for 8 is about -2.55 kg. Seven hundred fifty for 4 is about -2.73 kg. Six hundred for 2 is about -1.09 kg. Two hundred fifty for 16 weeks is about -3.64 kg. Same 7700 constant as the deficit page, only the horizon is in weeks.
If you skip weeks or type zero, the script treats it as one week, the way it always has. A zero deficit is allowed and gives a zero change. The US switch can show pounds from the same kilogram value. The formula still divides by 7700 kcal per kilogram.
Adherence, water, and glycogen break a straight line. The 7700 constant is an energy sketch per kilogram of tissue, not a promise about the morning scale. Two quieter eating weeks, or more salt, can hide the -1.09 kg from the 600 kcal example. A diet plan and a meal list are not built here.
Type 500 and 4, click Calculate, and you should see about -1.82 kg. Then keep 500 and type 1 to see -0.45 kg. Treat both numbers as a paper exercise for class, not as a promise from the bathroom scale.
How to use
- Type the daily deficit in kilocalories. Zero is fine. A negative number is not, because surplus lives on another calculator.
- Type the number of weeks. If you skip that field or type zero, the calculator counts one week, matching the existing script.
- Click Calculate. 500 kcal and 4 weeks give about -1.82 kg at the 7700 constant.
- Compute TDEE and Mifflin next door, then paste the difference you already know. This calculator has no energy profile.
- Open the calorie surplus calculator for gain from a surplus. This page stays with deficit times weeks.
Formula
Δkg = (-deficit × 7 × weeks) / 7700
Not a diet plan and not the weight gain calculator.
Daily deficit, weeks, and 7700
Mass change is minus deficit times 7 times weeks, divided by 7700. 500 kcal for 4 weeks is about −1.82 kg.
- deficit
- Daily kcal below maintain. 500 × 7 × 4 = 14000, 14000 / 7700 ≈ 1.82, and the minus sign makes −1.82 kg in this calculator.
- weeks
- How many weeks you multiply. One week at 500 kcal is about −0.45 kg; four weeks stack to about −1.82 kg.
- 7700
- The kcal-per-kg constant in this sketch. The calculator does not build a meal plan; it only divides deficit times days by 7700.
Examples
Example 2
- Deficit: 500 kcal/day
- Weeks: 1
-0.45 kg
500 kcal for 1 week gives about -0.45 kg.
Example 3
- Deficit: 300 kcal/day
- Weeks: 8
-2.18 kg
300 kcal for 8 weeks gives about -2.18 kg.
Example 4
- Deficit: 750 kcal/day
- Weeks: 4
-2.73 kg
750 kcal for 4 weeks gives about -2.73 kg.
Example 5
- Deficit: 350 kcal/day
- Weeks: 8
-2.55 kg
350 kcal for 8 weeks gives about -2.55 kg.
Example 6
- Deficit: 600 kcal/day
- Weeks: 2
-1.09 kg
600 kcal for 2 weeks gives about -1.09 kg.
Example 7
- Deficit: 1000 kcal/day
- Weeks: 1
-0.91 kg
1000 kcal for 1 week gives about -0.91 kg.
Example 8
- Deficit: 250 kcal/day
- Weeks: 16
-3.64 kg
250 kcal for 16 weeks gives about -3.64 kg.
Frequently asked questions
Is this the weight gain calculator?
No. Surplus on CalcBoxer is TDEE plus extra calories. Here a deficit times weeks over 7700, with a minus sign.
Why do 500 kcal and 4 weeks give about -1.82 kg?
Because 500 × 7 × 4 = 14000. 14000 / 7700 is about 1.82. The minus is the loss from a deficit.
Does this replace the calorie deficit page?
No. Deficit computes TDEE minus a daily cut. The calculator multiplies a deficit you already know by weeks. Two readings of the same 7700 constant.
What if I skip the week count?
The script uses 1 week. Zero weeks also falls back to one. You still need to type the deficit.
Does a negative deficit compute gain like a bulk?
No. The calculator rejects a negative deficit. Gain from a surplus lives on the calorie surplus calculator.
Does TDEE or Mifflin enter the -1.82 kg?
No. The inputs are deficit and weeks. You compute TDEE next door, then paste the difference here.
Why is 1000 kcal for a week only about -0.91 kg?
Because 1000 × 7 = 7000, and 7000 / 7700 is less than 1. A large weekly deficit is still not a kilogram on the nose.
Are water and glycogen inside the 7700 constant?
No. 7700 is an energy sketch per kilogram of tissue. Scale weight jumps with water. This is not a morning-scale promise.
Does US mode show pounds instead of kilograms?
Format.mass can show pounds from the same kilogram value. The formula still divides by 7700 kcal per kg.
What do I get at 300 kcal and 8 weeks?
About -2.18 kg. 350 for 8 is about -2.55, and 250 for 16 is about -3.64.
Knowledge sources
Change from a deficit and 7700 kcal/kg. This is a sketch, not a clinic scale.
Page updated in 2026.