Dietitians favor beam balance scales commonly called doctor’s scale that is used in your doctor’s office. You stand on a pad at the bottom of the scale and it has several weights that the nurse or dietitian moves until the beam balances level with you standing on the scale. This is the most accurate scale.
Other varieties are spring loaded scales that may have a digital display or a dial. The springs stretch with time so accuracy drops. Best bet is to stand on and off the scale 3 times. Each reading should be within 1 pound of each other. If not, buy a new scale.
Make sure your scale is level on a tile floor and calibrate the scale to zero with no weight on the scale, using the small dial on the scale if there is one. Then step on the scale, balancing your weight evenly and center on the scale. The humidity in most bathrooms does seem to affect the weight displayed by most scales.
Remember that body weight is relative and dependent on your level of hydration as well as the time of the menstrual cycle in women. It is not unusual for menstruating women’s weight to vary 3 to 5 pounds higher prior to their monthly flow as a woman’s body starts retaining fluid the week prior. Your lowest weight is in the morning with an empty stomach, after voiding the urine in your bladder and having a bowel movement. You can weigh yourself naked or lightweight clothing without shoes. Just be consistent so you can track the change in your weight over time rather than focusing on your weight that day. When your weight increases or decreases by 5 pounds or more, you should increase your food intake to gain weight or decrease your food intake to lose weight.
Bathroom scales are reviewed by Consumer Report. If you don’t subscribe to Consumer Reports, you can look at their buyers guide free in your local library reference area. According to CR, Health-O-Meter 840 ($50) and Counselor Digital 850 ($22) rated the best scale or Borg Hot Dots 9144 ($28). The Salter Electronic 971 ($50) rated the most accurate for repeatability in CR. Price did not seem to be a factor in the accuracy of bathroom scales. CR describes spring scales as working with “levers under the platform” which “transmit the force of your weight to a calibrated spring, which stretches in proportion to the weight imposed. The spring makes the scale’s dial or pointer move or governs the reading on the digital displays”. In spite of nice large digital displays, these scales are no more accurate than scales with a dial and pointer according to Consumer Reports, but digital displays are easier to read.