Alternatives and Comparisons
Compare popular peptide and weight calculators using dated, hands-on checks of their methods, sources, strengths and limitations.
None of the tools below is affiliated with FreePeptideCalc. Nothing here is repeated from someone else’s comparison: each page says what was loaded, on what date, and what it returned — and each one names what the other tool does better, because a comparison that never concedes anything is not worth reading.
How each comparison was made
Comparison pages are the easiest thing on the internet to write badly, because nothing forces the writer to have opened the other product. Two rules apply to every page here, and they are stricter than the rules governing the rest of the site precisely because these pages are about other people’s work.
- Nothing is second-hand. Every claim about another tool was produced by loading that tool on a stated date and recording what it returned. Each page prints both the date and the method in one sentence, so you can repeat the check rather than take our word for it. Claims about other people’s live products go stale faster than anything else here, which is why the date is on the page rather than in a comment.
- Every page concedes something. Each comparison names what the other tool does better, and a page that could not name anything would not ship. Across these 4 comparisons that comes to 11 specific points where another tool beats this one. A comparison that never concedes is an advertisement with a table in it.
Three assumptions this site used to carry did not survive that process. Losertown turned out not to be a naive 3,500-kcal line — it recalculates maintenance as weight drops, and its only method citation is buried in an invisible HTML comment. SteroidPlotter already plots semaglutide, tirzepatide and retatrutide. And peptidecalculator.com is dead but not parked: its own authoritative nameserver returns NXDOMAIN. Each correction came from loading the thing rather than from reading about it.
Losertown
Losertown is still online and still works. Here is exactly what its projection table is doing and the one thing it gets wrong — with the same dated weight projection, rebuilt on a model that accounts for metabolic adaptation, right on this page.
Checked
SteroidPlotter
SteroidPlotter already plots semaglutide, tirzepatide and retatrutide — which surprises most people looking for a GLP-1 chart. What it does not do is tell you where any of its half-lives came from.
Checked
Omni Calculator's Peptide Calculator
Omni Calculator's peptide tool does the reconstitution arithmetic correctly and has something this site does not: a named medical reviewer. What it does not have is a sourced dose for any compound.
Checked
peptidecalculator.com
The domain peptidecalculator.com is registered but serves nothing: its own nameservers return NXDOMAIN, so there is no page to load. Checked 17 September 2026, with the method shown.
Checked
Sources
Where a comparison rests on something other than our own check of the live tool — a published paper, a registry lookup, a regulator document — it is listed here.
- Published studyThe Lancet 2011;378(9793):826–37· 2011-08-27Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight
- Published studyInternational Journal of Obesity 2013;37(12):1614· 2013Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong?
- Published studyAmerican Journal of Clinical Nutrition 1990;51(2):241–7· 1990-02Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals
- FDA labelFDA· 2026-03WEGOVY (semaglutide) injection and tablets — FDA prescribing information
- FDA labelFDA / DailyMed· 2026-05OZEMPIC (semaglutide) injection — FDA prescribing information
- FDA labelFDA / DailyMed· 2026-08MOUNJARO (tirzepatide) injection — FDA prescribing information
- Published studyNew England Journal of Medicine· 2023Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — a Phase 2 Trial
- Published studyThe Lancet· 2022Urva S et al. LY3437943, a novel triple GIP/GLP-1/glucagon receptor agonist — phase 1
- FDA labelFDA / DailyMedEGRIFTA SV (tesamorelin) for injection — FDA prescribing information
- FDA labelFDA / DailyMedEGRIFTA WR (tesamorelin) for injection — FDA prescribing information and Instructions for Use
- ReferenceICANNICANN Registration Data Lookup Tool (domain registration and nameserver records)
- ReferenceInnovagen ABPepCalc.com — Peptide Property Calculator (sequence in; molecular weight, isoelectric point, extinction coefficient, net charge and solubility out)
- Published studyJournal of Computer-Aided Molecular Design 2016;30:271–277· 2016Lear S, Cobb SL. Pep-Calc.com: a set of web utilities for the calculation of peptide and peptoid properties and automatic mass spectral peak assignment