How accurate is the weight goal calculator?

Estimates only. Simple mode uses the 3,500 kcal/lb rule; Realistic mode adjusts for metabolic adaptation using Mifflin-St Jeor. Real loss varies with sleep, stress, and training.

What is the difference between Simple and Realistic mode?

Simple uses a flat 3,500 kcal per pound rule. Realistic recomputes BMR each week so projected loss slows down as you get lighter.

What is a safe weekly weight loss rate?

Up to about 1% of bodyweight per week is generally sustainable. Above that, more loss comes from lean mass.

Weight Goal Calculator

Estimate when you'll hit your target weight. Adjust, toggle, and plan.

Mode

Units

Current weight (lb)

Daily calorie deficit

Mild 250 · Moderate 500 · Aggressive 750

Project by

Show rows

Goal weight (lb)

Height (cm)

Age

Sex

Activity

Reach around

Weekly loss: · % bodyweight/wk

Period	Date	Weight	Δ Total	Δ Period

Estimates only. Real loss depends on sleep, stress, water, training, and individual variation — and metabolism adapts as you lose weight. The only way to know what you’re actually losing (fat vs. lean) is to measure it.
Book a DEXA scan →

How it works

The Simple mode applies the classic 3,500 kcal per pound (7,700 kcal/kg) rule — your daily deficit multiplied over time gives a straight-line projection. It’s quick, but optimistic, because it assumes your calorie burn never changes.

The Realistic mode uses the Mifflin–St Jeor equation to estimate your BMR each week, then multiplies by your activity level to get your current TDEE. As you lose weight, your TDEE drops, which means the same intake produces a smaller deficit — and your loss curve flattens. This is called metabolic adaptation, and it’s why most real diets stall.

A sensible weekly rate

A sustainable rate is roughly 0.5–1% of bodyweight per week. Faster than that and you start losing more lean mass, feel worse, and rebound harder. The calculator flags aggressive rates automatically so you can ease off the deficit.

Why a calculator is no substitute for measurement

Scale weight is a noisy signal. It can’t tell you if you’re losing fat, muscle, or water. A DEXA scan measures body composition directly — fat mass, lean mass, bone density, and regional distribution — so you can verify the calculator’s estimate against reality. That’s how you know if your plan is actually working.