Why are you taller in the morning?

What the studies found

Reilly, Tyrrell and Troup (1984) followed eight adult men over a day and found a peak-to-trough stature difference of 19.3 mm, about 1.9 cm. The highest reading was on waking; the lowest was before bed. This small study does not establish a fixed daily change for everyone.

Tyrrell, Reilly and Troup (1985) examined eight young adults and the effects of spinal loading. Their work also found daily variation and related it to loading and recovery. These studies describe temporary changes in stature, not overnight bone growth.

Why two readings can disagree

A day spent upright loads the spine; lying down reduces that load and allows recovery. Time of day is one reason two careful height measurements can differ. Posture, footwear and the way the head is aligned can add separate differences.

Do not add a standard amount to an evening measurement and call it your morning height. The amount differs by person and conditions. Record when and how each reading was taken instead.

Make your own readings comparable

Use the same level floor, wall or height measure, no shoes, and the same head position. Repeat at a similar time of day. Record a morning and evening reading separately if the daily change is what you want to compare.

A small short-term difference does not by itself prove lasting growth or height loss. For a visual comparison, put your own readings into the chart and label them by time. The chart illustrates your inputs; it does not diagnose a change.

Try the same example

Compare your morning and evening readings. The names, units and values carry into the editable chart.

For the arithmetic alone, use the height difference calculator. For a different unit, use the height converter.

The next useful step

• How to measure height consistently
• Why height sources disagree

How the charts work explains the shared scale, source precision and custom inputs.