Pre-Op Weight-Loss Target Calculator

There's no universal number — it depends on the target your own surgeon or insurer sets. Many teams use a BMI cut-off, commonly around 40 for elective operations like joint replacement or hernia repair, but yours may use 35 or 30, or none at all. This calculator works out the weight you'd need to lose to reach a chosen target BMI, but your team sets the actual goal for you.

A steady, healthy pace is usually about 0.5 to 1 kg (1 to 2 lb) per week. Losing faster than that is hard to sustain and can mean losing muscle and nutrients you need to heal well. This tool compares the pace your date would require against that safe range, so you can see whether the timeline is comfortable, aggressive, or unrealistic — and talk options through with your team.

Not automatically. A higher BMI can raise some risks, so teams may ask for weight loss to make surgery safer, but the final decision is theirs and depends on your whole picture. Even a modest loss lowers anaesthetic and wound-healing risk, so it's worth doing what you can. If the date is too tight, talk to your team about timing or other medical options rather than assuming the worst.

That happens, and it's worth a calm conversation with your team. They may adjust the surgery date, set a more achievable interim goal, or discuss medical options for weight management. Even partial progress helps. There are also medication routes to ask about — see our guide on GLP-1 medicines (like Ozempic) before surgery.