GLP-1 Goal Weight Calculator: Healthy BMI Range for Your Height

1. Enter your height in feet and inches, or in centimeters, and your weight today.
2. Read your milestones at 5, 10, 15 and 20%, where the SURMOUNT-1 and STEP 1 averages would leave you, and the healthy BMI range for your height, each with the loss in pounds and percent.
3. Drag the goal to any weight to see the loss it needs, its BMI and how many people in the trials reached a loss that size. If your goal sits above the healthy range, the calculator also shows the NICE waist target for your height. If you are from a background NICE sets lower cut-offs for, switch them on.
4. The four classic ideal-weight formulas, which use your sex, are under "Classic ideal-weight formulas".

The healthy range is BMI × height in meters squared, worked at 18.5 and 24.9. At 5 ft 5 in (1.651 m): 18.5 × 1.651² = 50.4 kg (111 lb), and 24.9 × 1.651² = 67.9 kg (150 lb).

The loss to reach the top of the band is 1 − 24.9 ÷ your BMI. Height cancels out, so the percentage depends only on where you start.

Worked example: 220 lb (99.8 kg) at 5 ft 5 in is a BMI of 99.8 ÷ 2.726 = 36.6. The loss to reach BMI 24.9 is 1 − 24.9 ÷ 36.6 = 32%. The SURMOUNT-1 average for tirzepatide 15 mg, 20.9%, would leave 220 × 0.791 = 174 lb, a BMI of 29.0 (Jastreboff et al., NEJM 2022). The STEP 1 average for semaglutide 2.4 mg, 14.9%, would leave 187 lb, a BMI of 31.2 (Wilding et al., NEJM 2021).

Each row is 1 − 24.9 ÷ the starting BMI, compared with the SURMOUNT-1 tirzepatide 15 mg mean of 20.9% and the STEP 1 semaglutide 2.4 mg mean of 14.9%.

The tirzepatide mean reaches BMI 24.9 only from a starting BMI of 24.9 ÷ 0.791 = 31.5 or lower. The semaglutide mean reaches it from 24.9 ÷ 0.851 = 29.3 or lower.

Both trials started from an average BMI near 38. SURMOUNT-1 reported a mean baseline weight of 104.8 kg and BMI of 38.0, with 94.5% of participants at BMI 30 or above (Jastreboff et al., NEJM 2022). STEP 1 started at 105.3 kg and BMI 37.9 (Wegovy prescribing information, section 14, Study 2).

The last column is arithmetic on two reported means, 38.0 × 0.791 and 37.9 × 0.851, not a result either trial published. From BMI 37.9, reaching 24.9 takes a 34.3% loss, so the semaglutide mean covered 14.9 ÷ 34.3 = 43% of the distance. The tirzepatide mean covered 20.9 ÷ 34.5 = 61%.

Individual results sat well either side of those means: in SURMOUNT-1, 57% of people on 15 mg lost 20% or more (Jastreboff et al., NEJM 2022). The GLP‑1 weight loss calculator shows how the loss builds month by month. If your weight stops moving well short of your target, work through what to check during a plateau in order.

Each classic formula is a base weight plus a fixed amount for every inch above 5 feet. The constants below are as tabulated by Peterson et al., American Journal of Clinical Nutrition 2016.

Hamwi was published in pounds. The calculator uses a rounded metric form: 45.5 kg + 2.2 kg per inch for women and 48 kg + 2.7 kg per inch for men. At 5 ft 5 in it reads 0.4 lb below the pound version, and at 5 ft 10 in 0.7 lb below. Below 5 feet, the calculator treats the inches above 5 feet as zero, so every shorter height returns the base weight; use the BMI range instead at those heights.

The table gives the calculator’s results at two heights. The healthy range is rounded to whole pounds, as the calculator shows it.

The four formulas spread over 7.5 lb at 5 ft 5 in and 10.3 lb at 5 ft 10 in. Converted back to BMI, they give 20.7 to 22.0 for the woman and 22.2 to 23.7 for the man, so none reaches the top of the healthy band. Peterson and colleagues found the same pattern: each of these four formulas lines up best with a BMI between 21.0 and 23.4, and they describe past equations as "misaligned with BMI values" (Peterson et al., 2016).

The CDC applies the adult BMI categories to people aged 20 and older (CDC adult BMI categories). NICE in the UK adds three limits (NICE guideline NG246, recommendations 1.9.11 to 1.9.13):

• For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, overweight starts at BMI 23 and obesity at 27.5.
• BMI should be read with caution in adults with high muscle mass.
• It should also be read with caution in people aged 65 and over.

The calculator uses the 18.5 to 24.9 band unless you switch on the NICE cut-offs. NICE also classifies waist-to-height ratio, and advises keeping your waist to less than half your height, a ratio under 0.5 (NICE NG246, recommendations 1.9.14 and 1.9.15). For adults with a BMI under 35, that classification applies across ethnic groups and to people with high muscle mass, so a tape measure gives a second target that still works in those groups.

The scale also cannot show what the lost weight was made of. In DXA scan sub-studies, 25 to 39% of the loss is lean mass (Look et al., 2025; Mozaffarian et al., 2025). Zepbound vs Wegovy muscle loss compares the two scans and what protects lean mass.