Calculator
What the Weight Loss Calculator does
Weight Loss Calculator: calculates Weeks to Goal, Suggested Daily Calories and Daily Deficit from Current Weight, Goal Weight and Target Loss / Week. Example: current weight 80 kg, goal weight 70 kg and target loss / week 0.5 kg gives weeks to goal 20.0.
Give the Weight Loss Calculator your Current Weight, Goal Weight, Target Loss / Week and Daily Maintenance Calories and it works out Weeks to Goal, Suggested Daily Calories and Daily Deficit. Change any input and the output follows immediately.
Knowing how a figure is derived makes it much easier to interpret sensibly. That is usually what brings readers checking a number from a clinic here.
Because it is all local, the tool is as fast as your device and as private as your own notes.
The field table, the method and a worked example are documented after the tool for anyone who wants to check the working.
What do the Weight Loss Calculator fields mean?
The Weight Loss Calculator uses 4 inputs. None of the boxes start empty. The page loads with a worked set of values you can edit or replace.
| Field | What to enter | Default |
|---|---|---|
| Current Weight | measured in kg; accepts 30 to 300 | 80 |
| Goal Weight | measured in kg; accepts 30 to 300 | 70 |
| Target Loss / Week | measured in kg; accepts 0.1 to 1.5 | 0.5 |
| Daily Maintenance Calories | measured in kcal; accepts 1000 to 5000 | 2200 |
How does the Weight Loss Calculator work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same calculation.
Validation runs before the calculation, which is why a mistyped value shows an error rather than a plausible-looking result.
Worked example
These are the values the Weight Loss Calculator loads by default, and the result it produces from them. Open the tool above and you will find precisely these figures already in place.
| Current Weight | 80 kg |
|---|---|
| Goal Weight | 70 kg |
| Target Loss / Week | 0.5 kg |
| Daily Maintenance Calories | 2200 kcal |
| Weeks to Goal | 20.0 |
|---|---|
| Suggested Daily Calories | 1,650 |
| Daily Deficit | 550 |
| Plan | Losing 10.0 kg at 0.5 kg/week takes about 20 weeks. Aim near 1650 kcal/day (from a 550 kcal deficit). |
Read next: Understanding BMI: What the Number Measures, and What It Misses
How to use it
- Set Current Weight in kg (30 to 300).
- Put Goal Weight in kg (30 to 300).
- Key in Target Loss / Week in kg (0.1 to 1.5).
- Fill in Daily Maintenance Calories in kcal (1000 to 5000).
- Because there is no round trip to a server, updating on every keystroke costs nothing.
- Check Weeks to Goal, Suggested Daily Calories, Daily Deficit and Plan on the right.
- Use Copy Link if you want the same setup again later, or Print for a paper copy.
What this tool does not do
- These formulas come from population averages and cannot account for your medical history.
- This is a screening estimate, not a diagnosis.
- Treat it as a fast first pass, not as the final word on a decision that matters.
- The tool trusts your numbers completely, so a mis-keyed digit propagates straight through.
Frequently asked questions
Enter Current Weight in kg, Goal Weight in kg, Target Loss / Week in kg and Daily Maintenance Calories in kcal. Every input names its unit, and every output does too, which removes the usual source of error.
Current Weight accepts 30 to 300 kg. Go outside it and you get an error against that specific field instead of a misleading number.
With the values loaded when the page opens, weeks to goal comes out as 20.0. Nudge one field at a time to see which one the answer is most sensitive to.
No. The work runs in JavaScript inside this page, so your values never leave your device. You can confirm it in your browser network tab.
Free for any use, personal or commercial.
It reports what the standard equation gives. Clinicians treat that output as one input among many, alongside history, examination and labs, and so should you.