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Set your scale on a hard surface.

Have you ever looked down at the scale and wondered if it’s the correct number? It’s a common occurrence, because you might be making one of these ten common mistakes when you weigh yourself.

Weighing yourself seems like a fairly straightforward procedure. You hop on the scale, see what it says, hop off and get on with your day. As simple as that sounds, there are some common mistakes that people make when they weigh themselves. Here are a few tips to help you weigh yourself correctly.

10 Common Mistakes in Weighing Yourself

Weighing yourself too often

It’s normal for weight to fluctuate from day to day by as much as a 5 pounds (or a couple of kilos). Most weight fluctuations are due to fluid shifts, and it may also have to do with what you recently ate. For instance, if you eat a salty meal at night, your body might retain some extra fluid—and you’ll see an uptick on the scale in the morning. On the other hand, cutting back too far on your carbohydrate intake can cause a temporary water loss, which may make you appear lighter on the scale. Recognize these shifts for what they are, and try to weigh yourself less frequently. It will be easier for you to see how your weight is trending over time. And for women only: know that fluid retention during your menstrual cycle may give you the false impression that you’ve gained body weight. You may want to avoid the scale during your cycle.

Not including the weight of your clothes

When you don’t weigh yourself at home, you may not know how to adjust for your clothing. You may tell yourself that your clothes weigh a lot more than they actually do. An article¹ published recently actually shed some light on this topic. Researchers weighed 35 women and 15 men—wearing only their indoor clothing, but no shoes—four times during a one-year period and averaged the clothing weight for each person. Men’s clothing on average was heavier than women’s, and, interestingly, the clothing weight didn’t vary all that much throughout the year. From their findings, it was suggested that women make a weight adjustment for clothing of about 1.75 pounds (0.8 kg), and men should make an adjustment of about 2.5 pounds (1.2 kg).

Focusing only on your weight, not body composition

Keep in mind that your weight on the scale is only that. You may know how much your total body weighs, but what really matters is your body composition. A person who carries a lot of muscle could be “overweight” according to a height and weight chart. But a body composition analysis would likely reveal a healthy body fat percentage, and that they’re actually at an appropriate weight. On the flip side, someone who is “thin on the outside but fat on the inside” might have a normal weight on a height and weight chart, and yet they could be carrying an unhealthy amount of body fat.

Weighing yourself at night

If you’re one of those people who hops on the scale several times a day, you’ve probably noticed that your weight can shift quite a bit from morning to night. Among other things, the extra weight comes from foods and fluids you’ve eaten all day. Ideally, you should weigh yourself first thing in the morning, without clothing, after you’ve emptied your bladder.

Using more than one scale

You’d think all scales would give you the same reading, but that’s often not the case. I can’t tell you how often I’ve weighed a client in my office, only to have them say, “I don’t weigh that much at home!” Scales do vary, so track your progress by using readings from only one instrument. The actual weight is one thing: what really matters is the direction in which your weight is moving. If you weigh on the same instrument all the time, you’ll get a more accurate sense of what your weight is doing over time.

You don’t have a decent scale

That said, if you’re going to keep a scale at home, do invest in a reliable instrument. Digital scales tend to be more reliable than the old-fashioned spring scales. Take time to read reviews before you buy.

Scale not set on a hard floor

Scales are designed to rest on a hard surface, like a wood or tile floor. If your scale is sitting on a throw rug or carpeted floor, it may not sit evenly on the floor and you may get an inaccurate reading.

Weighing yourself on Mondays

If you’ve been reading my posts regularly, you probably know that I often suggest that people weigh themselves on Friday mornings, not on Mondays. Here’s why: Most people have a more consistent structure to their eating during the week than they do on the weekend. If they’ve been trying to keep their calories in check, their weight is often at its lowest point for the week on Friday. I think this can really motivate you to stay on track over the weekend. But if you blow it on the weekend, your weight could be at its highest point on Monday morning, and the damage is already done.

Weighing yourself after exercise

After a workout, there’s a good chance that you’ve experienced some fluid losses, so your weight might be down. Since you’re not adequately hydrated, you won’t be getting an accurate body weight. The only reason to weigh yourself after exercise is if you’re trying to keep tabs on your fluid losses during exercise. Some athletes weigh themselves before and after exercise so they know how much fluid they need in order to replenish their losses. Every 2 pounds (1 kg) lost during activity represents 4 cups (1 liter) of fluid that needs replacing.

You let the numbers affect your mood

If the reading on the scale is disappointing to you, don’t let it ruin your whole day. Keep in mind that whenever you weigh yourself, you’re simply capturing a moment in time. Like your blood pressure or your cholesterol level, it’s just a reading that tells you where you are—it’s not a judgment of who you are. Keep tabs on your weight to follow the trend, but don’t judge your progress solely by what the scale is telling you. In the long run, the everyday healthy habits that you establish will bring you closer to your goal. So, keep your focus on all the positive changes you’re making, and let your weight take care of itself.

¹Whigham LD et al. Int J Obesity. 37:160; 2013.