Add the measurements, then divide by the count
The calculator uses every valid positive number in each field. It adds those measurements and divides by the number entered. It then subtracts the earlier average from the recent average.
For the full method, examples, and research context, read how to calculate weekly average weight.
A missing day is not zero
You can calculate an average with fewer than seven measurements. The result should be labeled with the number included, and two weeks with similar coverage are easier to compare. Do not enter zero for a missed weigh-in.
An arithmetic average is not every app's trend weight
This tool gives each entered measurement equal weight. Other apps may use rolling, weighted, or smoothed calculations. Their trend number can differ from this weekly mean without either calculation being broken.
Use the weight change percentage calculator when you want to express the difference relative to starting weight. Once you have comparable averages across a longer window, the TDEE from weight change calculator can make a rough retrospective estimate from complete calorie logs.
Make the weigh-ins comparable
An average is only as good as the measurements in it, and most of the noise people blame on their body is really measurement conditions.
Weigh at the same point in your routine: first thing, after the toilet, before eating or drinking, in similar clothing or none, on the same scale on the same hard floor. A scale on carpet can read differently from the same scale a metre away on tile.
You do not need to weigh every day for this to work. Three or four comparable mornings a week produce a usable average. Seven inconsistent ones produce a worse number than four careful ones.
Comparing one week with the next
The point of averaging is to compare periods rather than days. Put this week beside last week, not Tuesday beside Monday.
Even then, one week against one week is a thin comparison. Two averages separated by at least two weeks give the trend room to show above normal fluctuation. If you want the difference expressed as a rate rather than a raw number, the weight change percentage calculator converts it, and once you have complete intake data alongside it the TDEE from weight change calculator turns the pair into an observed maintenance estimate.
What an average cannot tell you is what changed. A lower average means the recent measurements were lower. It does not separate fat, water, glycogen or gut contents, and no scale can.
Read direction, not body composition
Water, food in the digestive tract, sodium, carbohydrate intake, training, menstrual-cycle changes, illness, and weigh-in timing can move scale weight. A lower weekly average does not prove an equal amount of body fat was lost.
Daily weighing is optional. If weighing or numerical tracking causes distress, compulsive checking, or eating-disorder symptoms, stop and speak with a qualified clinician.