How do I calculate cost per pound lost on a GLP-1?

Divide your monthly medication spend by the pounds you lost that month. For a stabler figure, divide your total spend since starting by your total loss since starting, which averages out the fast early months and the slow later ones. Use the amount you actually paid, including recurring consultation fees if those are part of the cost.

Why does my cost per pound change so much month to month?

Because weight loss is front-loaded. The same spend buys several pounds early on and a fraction of a pound near a plateau, so the ratio worsens over time even when nothing about your treatment has changed. A figure from month two flatters the treatment and a figure from month ten punishes it.

What is a realistic average monthly loss to enter?

Across the full trial period the published results work out at roughly two to three pounds a month for a 220 lb starting weight: −14.9% over 68 weeks for semaglutide 2.4 mg in STEP 1, and −15.0% to −20.9% over 72 weeks across the tirzepatide doses in SURMOUNT-1. Your first two months will likely beat that and your tenth will likely not. Enter your own average rather than a trial figure.

Why is the annual projection too optimistic?

The tool multiplies one month by twelve, which assumes the rate never changes. It does change: the trials above ran 68 to 72 weeks to reach their totals, and the last months contributed far less than the first. Treat the twelve-month figure as a ceiling, not a forecast.

Does cost per pound mean anything once I am maintaining?

No. At maintenance your monthly loss is near zero, so the division breaks down and the metric implies an infinite cost. The spend is still buying something at that point, which is the maintained weight loss, but this calculator cannot express it. Cost per pound only describes the losing phase.

Should I pick the medication with the lower cost per pound?

No. Prices vary too much by country, insurance, pharmacy and formulation for a single figure to generalise, and tolerability and supply matter more than price per pound. The one head-to-head trial, SURMOUNT-5, found −20.2% with tirzepatide against −13.7% with semaglutide at 72 weeks, but which medication is appropriate for you is a prescriber decision.

GLP-1 Cost per Pound Calculator

What each pound is really costing you in medication.

Monthly medication cost$Average monthly weight loss

Cost per lb lost

$50

Over 12 months

$4,800

Projected annual loss

96lb

A blunt but useful gut-check. Costs usually fall once you reach a maintenance dose, and weight loss slows toward a plateau — so early months look pricier per pound than the long-run average. Don't forget savings elsewhere (less takeout, fewer snacks).

The calculation, and what it contains

Cost per pound is your monthly medication spend divided by the pounds you lost that month. Nothing else. It does not include consultation fees, blood tests, needles, delivery, or the food you no longer buy, and it does not know what dose you are on. It is a gut-check on a single ratio, and the ratio is only as honest as the two numbers you feed it.

The weight-loss input is where it goes wrong. Enter a good month and the tool will multiply that month by twelve and hand you an annual projection. Weight loss is not linear, so that projection is the most optimistic number on the page.

What the trial numbers say a real year looks like

Take a 220 lb (100 kg) starting weight and apply the published trial results, which run for roughly 68 to 72 weeks — about sixteen months, not twelve.

Trial arm	Weight change	From 220 lb	Duration	Average per month
Semaglutide 2.4 mg (STEP 1)	−14.9%	−32.8 lb	68 weeks	2.1 lb
Tirzepatide 5 mg (SURMOUNT-1)	−15.0%	−33.0 lb	72 weeks	2.0 lb
Tirzepatide 10 mg (SURMOUNT-1)	−19.5%	−42.9 lb	72 weeks	2.6 lb
Tirzepatide 15 mg (SURMOUNT-1)	−20.9%	−46.0 lb	72 weeks	2.8 lb

Averaged across the whole trial, that is roughly two to three pounds a month. Those are separate trials in different populations, so the rows are not a head-to-head comparison — the one direct comparison, SURMOUNT-5, put tirzepatide at −20.2% against semaglutide at −13.7% at 72 weeks in 751 people, open-label.

The trap: the month you happen to measure

Loss is front-loaded. The early months run well above the trial average and the later ones well below it, because the curve flattens as you approach a plateau. The consequence for this calculator is direct: a cost-per-pound figure computed in month two will look far better than the identical spend computed in month ten, and neither is your real number.

The annual projection makes the same error twice over. Take the 8 lb a month this tool opens with, hold it for twelve months, and you get 96 lb — from a 220 lb start that is a 44% loss, more than double the largest trial average in the table, achieved in less time. Eight pounds in a good early month is entirely plausible. Eight pounds in month eleven is not, and the multiplication assumes it.

So use an average over several months rather than your best one, and recompute it as you go. If you want a figure you can act on, divide your total spend since starting by your total loss since starting. That single division absorbs the fast months and the slow ones and cannot be gamed by picking a flattering window.

Where the metric breaks entirely

At maintenance, cost per pound stops working. Your loss per month approaches zero, so the division approaches infinity — the tool will refuse to compute it, and by its own logic your medication has become infinitely expensive on the exact regimen that is holding the result you paid for. That is the flaw in the metric, not in the treatment. Cost per pound measures a phase, not a therapy.

The same blind spot applies to everything a pound does not capture. Two people can lose the same 30 lb and get very different value from it depending on what else changed. Nothing on this page prices that, and no calculator that divides money by pounds can.

Why this page has no prices in it

Because a published price would be wrong for most people reading it. What you pay depends on country, insurance or NHS route, pharmacy, whether the product is branded or compounded, dose, pack size, and any manufacturer savings programme you qualify for — and it changes as you titrate, usually upward as the dose climbs.

You have to bring your own cost figure, so bring the whole one. Use the amount that actually left your account last month: the medication itself, any recurring consultation or subscription fee tied to the prescription, needles and sharps disposal if you buy them separately, and delivery. Leaving those out understates the cost of every pound by whatever they add up to, and they are the part of the bill that does not fall when you reach a maintenance dose.

One caution on how you use the output. A lower cost per pound does not identify the better medication for you. Tolerability, supply, existing conditions and what your prescriber will actually prescribe all outrank it, and the cheapest option you cannot stay on has an infinite cost per pound. Bring the number to a conversation about affordability; do not let it pick the drug.

Frequently asked

How do I calculate cost per pound lost on a GLP-1?: Divide your monthly medication spend by the pounds you lost that month. For a stabler figure, divide your total spend since starting by your total loss since starting, which averages out the fast early months and the slow later ones. Use the amount you actually paid, including recurring consultation fees if those are part of the cost.
Why does my cost per pound change so much month to month?: Because weight loss is front-loaded. The same spend buys several pounds early on and a fraction of a pound near a plateau, so the ratio worsens over time even when nothing about your treatment has changed. A figure from month two flatters the treatment and a figure from month ten punishes it.
What is a realistic average monthly loss to enter?: Across the full trial period the published results work out at roughly two to three pounds a month for a 220 lb starting weight: −14.9% over 68 weeks for semaglutide 2.4 mg in STEP 1, and −15.0% to −20.9% over 72 weeks across the tirzepatide doses in SURMOUNT-1. Your first two months will likely beat that and your tenth will likely not. Enter your own average rather than a trial figure.
Why is the annual projection too optimistic?: The tool multiplies one month by twelve, which assumes the rate never changes. It does change: the trials above ran 68 to 72 weeks to reach their totals, and the last months contributed far less than the first. Treat the twelve-month figure as a ceiling, not a forecast.
Does cost per pound mean anything once I am maintaining?: No. At maintenance your monthly loss is near zero, so the division breaks down and the metric implies an infinite cost. The spend is still buying something at that point, which is the maintained weight loss, but this calculator cannot express it. Cost per pound only describes the losing phase.
Should I pick the medication with the lower cost per pound?: No. Prices vary too much by country, insurance, pharmacy and formulation for a single figure to generalise, and tolerability and supply matter more than price per pound. The one head-to-head trial, SURMOUNT-5, found −20.2% with tirzepatide against −13.7% with semaglutide at 72 weeks, but which medication is appropriate for you is a prescriber decision.

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Sources

STEP 1 — Once-Weekly Semaglutide in Adults with Overweight or Obesity (NEJM 2021) — Semaglutide 2.4 mg: −14.9% body weight at week 68 versus −2.4% with placebo; 1,961 participants
SURMOUNT-1 — Tirzepatide Once Weekly for the Treatment of Obesity (NEJM 2022) — Tirzepatide 5, 10 and 15 mg: −15.0%, −19.5% and −20.9% at week 72 versus −3.1% with placebo; 2,539 participants
SURMOUNT-5 — Tirzepatide versus Semaglutide head-to-head (NEJM 2025) — Open-label direct comparison: −20.2% with tirzepatide versus −13.7% with semaglutide at week 72; 751 participants

Medical disclaimer. Tiro is a tracking companion, not a medical device, and nothing on this site is medical advice. Always follow the titration schedule and dosing instructions from your prescriber. Never change your dose without talking to them first.