If you don't have a scale, you can estimate your weight and track body changes using a few alternative methods. The most accurate non-scale method is using a measuring tape to track the circumference of your waist, hips, neck, and chest; changes in these measurements are often a better indicator of health and body composition than raw weight. Another method is the "displacement" technique based on Archimedes' Principle: if you have a full bathtub, you can mark the water level, submerge yourself, and then calculate the volume of water displaced, though this requires complex math to convert volume to mass. You can also use a "benchmark" item, such as a pair of non-stretch denim jeans; how they fit around the waist and thighs can tell you if you are gaining or losing mass. Finally, some high-end fitness apps can provide a rough estimate of body mass by analyzing a 360-degree video or photo of your body using AI, though these are "estimates" rather than precise measurements. For most, tracking energy levels and physical dimensions is a more productive health metric than knowing a specific number of pounds.