Weight Loss Percentage Calculator

A weight loss percentage calculator turns two weigh-ins into one comparable number: the percentage of weight loss, measured against your starting body weight. Divide the pounds lost by the starting weight and multiply by 100. Going from 220 lb to 202 lb is an 18 lb drop, which works out to 8.18% of the starting weight. Health guidelines set goals in exactly these terms: NHLBI and the 2013 AHA/ACC/TOS obesity guideline recommend a first goal of 5% to 10% of starting weight within about 6 months.

This page measures what has already happened. If you want to plan ahead instead, the Weight Loss Calculator builds a calorie target and a dated timeline to a goal weight, the Calorie Deficit Calculator finds the daily deficit for a chosen pace, and the BMI Calculator tells you where your current weight sits on the height-adjusted scale. Use this calculator to score progress you have made; use those to decide what to do next.

The percent weight loss formula

The calculation is a simple ratio. Because both weights are in the same unit, the unit cancels and the answer is the same in pounds or kilograms:

Two follow-on numbers come from the same inputs. Weight lost is just the difference between the two readings. The weekly rate divides that difference by the number of weeks between weigh-ins, and dividing the percentage by the weeks gives the rate as a percent per week. The milestone targets run the formula backwards: the weight at a 10% loss is the starting weight × 0.90.

Worked example: 220 lb to 202 lb in 12 weeks

Here is every step for someone who weighed 220 lb on day one of a program and 202 lb twelve weeks later:

In metric the same person went from 99.8 kg to 91.6 kg, an 8.2 kg loss, and the percentage is unchanged at 8.18%. At the current 1.5 lb per week pace, the remaining 4 lb to the 10% milestone would take a little under three more weeks, if the pace held.

Percent lost by starting weight

The same number of pounds means a very different percentage depending on where you started. The table runs the formula for four common amounts lost:

Twenty pounds is a 13.3% loss at 150 lb but only 6.7% at 300 lb. This is why percentages, not pounds, are the fair way to compare two people or to judge whether you have hit a health-relevant threshold.

Weight at 5%, 10% and 15% loss

NHLBI frames the first goal as a loss of 5% to 10% of your initial weight over about 6 months. This table shows what that means on the scale for a range of starting weights, computed as starting weight × (1 − percent):

Notice that the first milestone is often smaller than people expect: a 250 lb adult reaches 5% at 237.5 lb, a loss of 12.5 lb, well before any number that looks like a "goal weight." The CDC uses the same kind of example: a 5% loss for a person who weighs 200 pounds is 10 pounds.

What the guidelines say about each milestone

• 3% to 5%: the 2013 AHA/ACC/TOS guideline says a sustained loss of this size is likely to bring clinically meaningful reductions in triglycerides, blood sugar, hemoglobin A1c and the risk of type 2 diabetes. NIDDK adds that losing at least 3% to 5% may reduce fat in the liver.
• 5% to 7%: NIDDK says people at risk may be able to prevent or delay type 2 diabetes by losing at least 5% to 7% of their starting weight, about 10 to 14 lb at 200 lb.
• 5% to 10% in about 6 months: the first goal recommended by NHLBI and the AHA/ACC/TOS guideline. Larger losses than 3% to 5% also lower blood pressure and improve LDL and HDL cholesterol.
• 15% and beyond: this calculator adds a 15% marker as a stretch milestone. It is not a separate guideline threshold; the guideline simply notes that greater weight loss brings greater benefits.

How fast is a healthy percentage per week?

The CDC says people who lose weight at a gradual, steady pace of about 1 to 2 pounds per week are more likely to keep it off. Expressed as a percentage it depends on your size: at 200 lb, 1 lb per week is 0.5% per week and 2 lb per week is 1.0% per week. The table below shows what 12 weeks at each pace adds up to, and how many pounds a "1% per week" pace equals at each starting weight:

A 150 lb person losing 2 lb per week is shedding 1.33% of their body weight weekly, a much bigger share than the same 2 lb for a 300 lb person (0.67% per week). The CDC's guidance is written in pounds, so at lower body weights its upper end is a larger slice of the body. Your own pace is something to discuss with a doctor if you are unsure it suits you.

How to use this weight loss percentage calculator

1. Pick your units. US units (pounds) are the default; switch to metric for kilograms. Your entries are converted when you switch, and the percentage stays the same.
2. Enter your starting weight. Use the weigh-in from the first day of the period you are measuring, ideally taken under the same conditions as today's reading (same scale, same time of day, before eating).
3. Enter your current weight. If it is above the starting weight the calculator flips to "gained" instead of "lost".
4. Add the weeks between weigh-ins (optional). This unlocks the weekly rate in both pounds and percent so you can compare your pace against the CDC's 1 to 2 lb per week. The quick buttons cover 4, 8, 12, 26 and 52 weeks.
5. Read the result. The big number is the percent of starting weight lost. Below it you get the absolute loss (with the other unit in brackets), the weekly rate, the three milestone cards and a ladder of target weights from 1% to 20%.

Who this calculator is for

• Anyone on a weight loss program who wants to know whether they have reached the 3% to 5% loss that guidelines call clinically meaningful, or the 5% to 10% first goal.
• Workplace and family challenges that rank participants by percentage so that a 150 lb and a 300 lb entrant compete fairly.
• Patients tracking a clinical target. Guidelines express goals as percentages, such as the 5% to 10% first goal or NIDDK's 5% to 7% for preventing type 2 diabetes, rather than as a fixed number of pounds.
• Coaches and trainers reporting client results in a size-neutral way.
• Athletes making weight who need to know what a 3% or 5% cut means on the scale from their walk-around weight.

Why percentages beat pounds in a challenge

Consider three people in the same 8-week contest. Person A starts at 250 lb and finishes at 235 lb: 15 lb lost, 6.00%. Person B starts at 160 lb and finishes at 150 lb: only 10 lb lost, but 6.25%. Person C goes from 195 lb to 181 lb: 14 lb, 7.18%. Ranked by pounds the order is A, C, B. Ranked by percentage it is C, B, A. Clinical guidelines describe weight loss the same way, as a share of starting weight, so the percentage ranking also lines up with how health benefits are measured.

Key terms

• Starting weight: the reference weigh-in that every percentage is measured against. It stays fixed for the whole program, even after you pass milestones.
• Percent of body weight lost: the loss divided by the starting weight. A 10% loss at 220 lb means the scale reads 198 lb.
• Weekly rate: total loss divided by elapsed weeks. Shown here both as lb (or kg) per week and as percent per week.
• Milestone: a percentage threshold with a health meaning attached. Guidelines use 3% to 5% (clinically meaningful) and 5% to 10% (first goal); this tool adds 15% as a stretch marker.
• Target weight at X%: starting weight × (1 − X ÷ 100). This is what the ladder table lists for every whole percent from 1 to 20.

What changes the result

• The starting weight you choose. Measuring from a years-old peak instead of the first day of your current program inflates the percentage and hides recent plateaus.
• Weigh-in conditions. Water, food and clothing all move the scale from day to day. At 150 lb, every 2 lb of such noise shifts the percentage by 1.3 points, so compare morning-to-morning readings.
• Time window. The percentage does not care how long it took, but the weekly rate does. Twelve weeks versus twenty weeks for the same 18 lb is 1.5 lb/week versus 0.9 lb/week.
• Body composition. Two people can lose the same 8% and have very different fat-versus-muscle results. The scale cannot tell them apart.
• Rounding. Scales that read in whole pounds can hide up to a half-pound; at 100 kg a 0.5 kg reading error changes the percentage by 0.5 points.

Tips for meaningful tracking

• Weigh in at the same time each week, first thing in the morning after using the bathroom and before breakfast.
• Record the starting weight on day one and never revise it; revising it resets your percentage and breaks comparability.
• Judge trends over 2 to 4 weeks rather than single readings. A rolling weekly average smooths water swings.
• Pair the percentage with a waist measurement or the Body Fat Calculator so muscle gain does not read as failure.
• Celebrate 5%. A sustained loss of 3% to 5% already brings clinically meaningful benefits, according to NHLBI and the AHA/ACC/TOS guideline, regardless of the "ideal" number on a chart.

Limitations

• The formula compares two scale readings only. It does not separate fat, muscle, bone or water, and it cannot assess health on its own.
• It makes no forecast. The weekly rate is the historical average between your two weigh-ins, not a prediction that the same pace will continue; NIH research shows that weight change slows as the body adapts (Hall et al., 2011).
• The milestones are guidance for adults with overweight or obesity. They are not targets for people already at a healthy weight, for children, or during pregnancy.
• The calculator reports your pace; it does not judge whether that pace is safe for you. The CDC links a gradual 1 to 2 lb per week with keeping weight off.
• This is an educational calculator, not medical advice. Talk to a doctor or registered dietitian before starting or changing a weight loss program.

Related calculators and when to use which

This page answers "how much of my body weight have I lost so far?" Use the Weight Loss Calculator when you want a forward-looking plan with a calorie target and a goal date, the Calorie Deficit Calculator when you already have a pace in mind and need the daily deficit to hit it, the BMI Calculator to see which weight category your current reading falls into, and the Ideal Weight Calculator for a height-based reference range. For the maintenance calories you will need once you reach a milestone, the Maintenance Calorie Calculator picks up where this one leaves off.

Sources

• National Heart, Lung, and Blood Institute (NHLBI, NIH): Aim for a Healthy Weight (lose 5% to 10% of initial weight over about 6 months; benefits of a 3% to 5% loss).
• Jensen MD, et al. (2014): 2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults, Circulation (3% to 5% clinically meaningful; first goal 5% to 10% within 6 months).
• Centers for Disease Control and Prevention (CDC): Steps for Losing Weight (gradual loss of about 1 to 2 lb a week; modest loss helps blood pressure, cholesterol and blood sugar; 5% of 200 lb is 10 lb).
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): Treatment for Overweight & Obesity (5% over 6 months as an initial goal) and Health Risks of Overweight & Obesity (at least 5% to 7% to prevent or delay type 2 diabetes; 3% to 5% for liver fat).
• Hall KD, et al. (2011): Quantification of the effect of energy imbalance on bodyweight, The Lancet (NIH model of how weight change slows over time).