The most reliable way to weigh carry-on luggage at home without a dedicated luggage scale is the "Differential Weighing" method using a standard bathroom scale. First, step on the scale alone and record your weight. Next, step back onto the scale while holding your packed carry-on bag. Subtract your initial weight from the total to find the weight of the bag. If the bag is too large to see the display, you can place a small stool or a flat box on the scale, "zero" it out (or subtract the stool's weight), and balance the bag on top. In 2026, some smartphones also offer AR (Augmented Reality) measurement apps that can estimate the volume of your bag to ensure it fits airline sizers, but these are less accurate for weight. Another "hack" is to use a simple broomstick balanced between two chairs as a makeshift scale, hanging a known weight (like a 5kg bag of flour) on one side and your luggage on the other to see which is heavier—though the bathroom scale method is much more precise for strict airline limits.