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BMI Weight Loss Calculator

Health

Find how much weight to lose to reach a target BMI, plus a safe timeline based on 1-2 lbs per week. Free calculator with weight-loss milestones.

Reviewed by the thecalcu.com team · Last updated July 13, 2026

Height67in
4884
Current Weight200lbs
70500
Target BMI24.9
18.527
Planned Weekly Loss1lbs/wk
0.52

Current BMI

—

Note: A safe, sustainable weight-loss rate is generally 1-2 lbs per week. Consult a doctor before starting any weight-loss plan, especially for larger amounts of weight.

What is a BMI Weight Loss?

A BMI Weight Loss Calculator turns the standard Body Mass Index formula around: instead of just telling you your current BMI, it works backward from a target BMI to tell you exactly how much weight to lose and roughly how long it will take at a safe, sustainable pace. It's the practical follow-up to the BMI Calculator, once you know your current BMI, this tool answers "what do I actually need to do about it?"

The calculator starts by computing your current BMI from your height and weight, using the same formula used across all standard BMI tools. It then calculates the exact weight that corresponds to your chosen target BMI for your specific height, giving you a concrete number in pounds rather than an abstract index value. From there, it projects a timeline based on a weekly weight-loss rate you control, capped at the medically recommended 1-2 lbs per week range.

This reverse-engineering approach, target outcome to required input, makes an otherwise abstract number actionable, turning "get my BMI under 25" into "lose 18 lbs over about 18 weeks."

Why Use a BMI Weight Loss Calculator?

Knowing your BMI is one thing; knowing what to actually do about it is another. This calculator closes that gap by converting a target BMI into a specific weight goal and a realistic timeline, so instead of an open-ended "lose weight" goal, you get "lose 18 lbs by mid-November at 1 lb per week."

It's especially useful when starting a new health plan, since seeing a concrete number and date makes the goal feel achievable rather than vague. Pairing the resulting weight target with the Calorie Calculator lets you translate the weekly loss rate into a specific daily calorie deficit, turning the plan into something you can act on immediately.

Who Should Use This Calculator?

Anyone starting a structured weight-loss plan benefits from seeing a concrete target weight and timeline rather than an open-ended goal. People working with a doctor or dietitian can use the output as a starting point for a conversation about realistic, medically sound targets. Fitness app users who want to set a milestone-based goal can convert the output into weekly checkpoints. Anyone whose current BMI is already healthy but wants to fine-tune toward the middle of the range can also use this to model smaller, incremental targets, and those planning weight gain instead should use the Ideal Weight Calculator instead.

What Insights Does the BMI Weight Loss Calculator Give You?

  • Current BMI, your starting point, calculated the same way as the standard BMI Calculator, showing where you are today.
  • Target Weight, the exact weight in pounds that corresponds to your chosen target BMI at your height, making the abstract BMI number concrete.
  • Weight to Lose, the direct difference between your current weight and target weight, in pounds, the number that actually drives your plan.
  • Estimated Weeks, a projected timeline based on your chosen weekly loss rate, giving you a realistic date range to work toward rather than an open-ended goal.

How to use this BMI Weight Loss calculator

  1. Enter your Height in inches using the slider or type an exact value.
  2. Enter your Current Weight in pounds using the slider or type an exact value.
  3. Set your Target BMI, most users aim for somewhere in the 22-24.9 healthy range.
  4. Set your Planned Weekly Loss rate, keeping it within the safe 1-2 lbs per week range.
  5. Review the result panel showing your Current BMI, Target Weight, Weight to Lose, and Estimated Timeline in weeks.
  6. Use the step-by-step breakdown to see exactly how the target weight and timeline were calculated.
  7. Combine the weekly loss target with the Calorie Calculator to determine your daily calorie deficit needed to hit the plan.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Step 1, Current BMI:

Current BMI = 703 × current weight (lbs) ÷ height (in)²

Step 2, Target weight (reverse BMI formula):

Target Weight = Target BMI × height (in)² ÷ 703

Step 3, Weight to lose and timeline:

Weight to Lose = Current Weight − Target Weight
Weeks to Goal = Weight to Lose ÷ Weekly Loss Rate

Worked example:

A person is 5'7" (67 inches) tall, weighs 200 lbs, targets a BMI of 24.9, and plans to lose 1 lb per week.

1. Current BMI = 703 × 200 ÷ 67² = 140,600 ÷ 4,489 = 31.3 (Obese range)
2. Target weight = 24.9 × 4,489 ÷ 703 = 158.9 lbs
3. Weight to lose = 200 − 158.9 = 41.1 lbs
4. Timeline = 41.1 ÷ 1 = 42 weeks (roughly 9.7 months)

Assumptions and limitations:

- Assumes a constant weekly loss rate; real-world weight loss typically slows over time and includes normal fluctuations and plateaus.
- Does not account for muscle mass changes, pairing gradual weight loss with resistance training helps preserve lean mass, but this calculator only tracks total body weight.
- Target BMI is capped between 18.5 and 27 to discourage unsafe extreme targets; always consult a healthcare provider for personalized weight-loss goals.

Frequently Asked Questions

How does the BMI Weight Loss Calculator work?
The calculator first computes your current BMI from your height and weight, then works backward from your chosen target BMI to find the exact target weight for your height. It subtracts that target from your current weight to show exactly how many pounds you need to lose, then divides that by your planned weekly loss rate to estimate a timeline.
What is a safe rate of weight loss per week?
Most health organizations, including the CDC, recommend losing 1 to 2 pounds per week as a safe and sustainable pace. Faster weight loss can lead to muscle loss, nutrient deficiencies, and a higher chance of regaining the weight, so this calculator caps the weekly loss input at 2 lbs per week.
What target BMI should I choose?
A target BMI between 18.5 and 24.9 falls within the standard healthy weight range, and many people aim for the middle to upper end of that range (around 22-24.9) as a realistic, sustainable goal. Your ideal target should ultimately be discussed with a doctor or dietitian, especially if you have a lot of weight to lose or existing health conditions.
Why does my target weight change when I change my target BMI?
Target weight is calculated directly from your target BMI and your height using the same formula as the reverse of the standard BMI calculation. Because BMI = weight ÷ height², a lower target BMI always corresponds to a lower target weight for the same height, and vice versa.
Is losing weight the same as improving health?
Not always, weight loss is one indicator among several, and improvements in body composition, blood pressure, and fitness can happen even without dramatic weight change. This calculator is a planning tool for a weight target, not a complete measure of health, and should be used alongside guidance from a healthcare provider.
Can I use this calculator to plan weight gain instead of loss?
This calculator is designed specifically for weight loss planning, calculating how much weight to lose to reach a lower target BMI. If your goal is healthy weight gain, the Ideal Weight Calculator and a calorie-surplus plan from the Calorie Calculator are better suited to that goal.
How accurate is the estimated timeline?
The timeline is a straightforward projection based on your chosen weekly loss rate remaining constant, which real-world weight loss rarely does exactly, plateaus and fluctuations are normal. Treat the estimate as a general planning guide rather than a guaranteed date, and expect actual progress to vary week to week.
What if my current weight is already below my target BMI weight?
If your current weight is already at or below the weight that corresponds to your target BMI, the calculator will show 'Already at goal' instead of a weight-loss target. In that case, setting a lower target BMI is not medically advisable unless specifically recommended by a healthcare provider.
Does this calculator account for muscle loss during weight loss?
The calculator only tracks total body weight relative to a BMI target and does not distinguish between fat loss and muscle loss. Combining a gradual weight-loss rate (1-2 lbs/week) with resistance training and adequate protein intake helps preserve muscle mass during the process, though this calculator does not model that directly.
Should I combine this calculator with a calorie tracker?
Yes, knowing how many pounds to lose is only half the plan; the Calorie Calculator or TDEE Calculator can help translate your weekly loss target into a daily calorie deficit. A 1 lb per week loss generally requires roughly a 500 calorie daily deficit, which these calculators can help you plan around your specific metabolism.
Is a lower BMI always better?
No, going below a BMI of 18.5 moves into the underweight category, which carries its own health risks including nutritional deficiencies and weakened immunity. The healthy range of 18.5-24.9 exists precisely because both extremes carry risk, so this calculator restricts target BMI inputs to a realistic 18.5-27 range.
Also known as
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