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Maybe Grandma in Lyon thinks in centimeters and Grandpa in Ohio thinks in feet and inches. You send a photo of the new mark, and half the family has to reach for a calculator. Getting the growth chart inches vs centimeters question right is mostly about habits: one measurement, one conversion, one label format that everyone can read.

This guide gives you the conversion table, the rounding rules, and a label template to copy onto your chart.

Inches or centimeters: which should be the "home" unit?

In short: the home unit is whatever is printed on your chart. Everything else is a translation of it.

Pick one unit as the source of truth and measure in it every time. The other unit is always calculated, never measured separately. This matters more than it sounds. Two tapes, two people and two readings give you two heights that differ by a few millimeters, and then the family debates which one is right.

Here are simple rules for choosing:

• Your chart is printed in inches: inches are home. Convert to centimeters for the label.
• Your chart is printed in centimeters: centimeters are home. Convert to inches.
• Blank wall or door frame: use the unit on the tape measure you own and will still own in five years.
• Your pediatrician records in one unit: that doesn't have to change your home unit. The wall chart is a family record, not a medical one.

Write the home unit first on every label. Years from now, that order tells anyone reading the chart which number was measured and which was converted.

Height chart: cm to inches and back

The math is one number. Multiply inches by 2.54 to get centimeters. Divide centimeters by 2.54 to get inches.

Feet and inches need one extra step. Turn the height into inches first: 3 ft 4 in is 36 + 4 = 40 inches, and 40 × 2.54 = 101.6 cm.

Inches to centimeters

For the fractions in between, add these: 1/4 inch is 0.6 cm, 1/2 inch is 1.3 cm, and 3/4 inch is 1.9 cm. So 39 1/2 inches is 99.1 + 1.3 = 100.4 cm, close enough to the exact 100.3.

Centimeters to inches (round numbers)

The eighths in this table are for lining up a scale, where a tighter figure helps. For the label on a child's mark, keep rounding to the nearest 1/4 inch.

Quick mental math for phone calls

When a relative asks mid-call and you have no calculator, these are close enough:

• Inches to centimeters: multiply by 2.5, then add 1 cm for a toddler or 2 cm for a school-age kid. For 40 inches: 100, plus a bit, is about 101 to 102 cm.
• Centimeters to inches: multiply by 4 and drop the last digit, then take off a half inch to an inch. For 100 cm: 40, minus a bit, is about 39 1/2 inches.

Use mental math for conversation only. What goes on the chart should come from a calculator or the tables above.

How to convert height measurements for a family chart without drift

Conversions go wrong in small, boring ways. These four rules prevent nearly all of them.

1. Always convert from the original. If you measured 41 1/4 inches, every centimeter figure comes from 41 1/4. Never convert a rounded number back again, because each round trip can shift it.
2. Round both units to a similar grain. A quarter inch and a half centimeter are roughly the same size step. Use the nearest 1/4 inch and the nearest 0.5 cm. Writing 104.78 cm suggests a precision that a wiggly four-year-old can't deliver.
3. Work out "how much they grew" in the home unit. Subtract last year's mark from this year's in the unit you measured, then convert the difference. From 38 inches to 40 3/4 inches is 2 3/4 inches of growth, which is 7 cm.
4. Don't correct old labels. If you change your rounding habit later, leave earlier marks alone. A chart with honest, slightly uneven labels is better than one that has been rewritten.

One more thing for families with a baby. Children under two are usually measured lying down, and that length reads a little differently from a standing height. If your first standing mark seems to "lose" a bit against the last baby number, that's the change in method. Our guide on when to start tracking your baby's height covers that handover.

The dual-unit labeling template

In short: one line on the chart, one label beside it, home unit first, month written as a word.

The date is the part most families get wrong. Written as 3/4/27, it means March 4 in the United States and 3 April in most other countries. Write the month as a short word and the problem disappears.

Copy whichever of these fits your chart. Each example assumes an inch chart, so inches come first. Flip the order if centimeters are your home unit.

The standard label:

Mila · 4 yrs · 14 Mar 2027 · 40 3/4 in / 103.5 cm

The compact label, for a crowded chart or several siblings:

Mila 4 · Mar 2027 · 40 3/4″ / 103.5

The three-way label, for relatives who think in feet and inches:

Mila · 4 yrs · 14 Mar 2027 · 3 ft 4 3/4 in · 40 3/4 in · 103.5 cm

The growth label, written small under the main one:

+2 3/4 in / +7 cm since last March

A matching mark log

Keep a paper or phone copy of every mark. It protects the record if the chart is ever damaged, and it is the thing you actually send abroad. Use these columns:

The "Measured in" column looks fussy. It is the one that settles arguments later, because it shows which number was read off the chart and which was calculated.

How to add a centimeter scale to an inch chart

Dual labels on each mark are enough for most families. Add a full second scale only if relatives who read centimeters will see the chart often, in person or in photos, and want to read heights without squinting at your handwriting.

You need a metric tape measure, a pencil, and a pen that suits your chart's material.

1. Lay the chart flat on a table or clean floor and smooth it out.
2. Line up the tape by the numbers, not the edge. Many charts don't start at zero. Slide the metric tape until its 76.2 cm line sits exactly on the chart's 30-inch line.
3. Check a second point. The 50-inch line should now sit at 127 cm. If it doesn't, the chart isn't lying flat or the tape has slipped.
4. Tick every 10 cm in pencil along the edge you don't use for height marks. Label each tick with just the number: 60, 70, 80.
5. Go over it in ink once every tick checks out against the round-number table above. Let it dry before rehanging.

Working the other way, on a centimeter chart? Tick each foot instead: 30.5 cm, 61.0 cm, 91.4 cm, 121.9 cm, 152.4 cm and 182.9 cm.

Our canvas charts begin at the 6-inch mark so they clear the baseboard, and they come with a fabric-safe pen that works for both the scale and the labels. If a relative abroad is hanging one with a metric tape, the 6-inch line belongs 15.2 cm above the floor.

Wherever the chart hangs, secure it firmly to the wall and keep it away from the crib. Keep pens capped and out of small hands between measuring days.

Making it a growth chart for a bilingual family

Numbers travel well. Words don't always. A few small choices keep the chart readable in two languages without cluttering it.

• Let symbols do the work. "cm" is written the same way almost everywhere. For inches, the double-prime mark (″) is widely understood where the abbreviation "in" is not.
• Add a small key once. Write the repeated words in both languages in a bottom corner, then use only numbers on the marks. For example: "yrs = años", "yrs = ans" or "yrs = Jahre".
• Use short month names both sides recognize. Mar, Sep and Nov read clearly across many languages. If one doesn't, write both, such as "Jan / ene".
• Mind the decimal mark. Many countries write 103,5 cm with a comma. Pick the style of your home unit for the chart, and use the reader's style in messages to them.
• Use the name everyone uses. If a child goes by one name with one side of the family and another with the other, write both on the first mark.

The chart is also a handy teaching tool once kids can count. Reading the same height in two units is a natural first lesson in measurement, and our height chart math activities are easy to adapt to both scales.

Sharing each new mark with family abroad

A photo of a mark on its own is hard to read from another continent. Send three things together: a close-up of the label, a wider photo of the child standing beside the chart, and one line of text with both units.

Lead with the reader's unit, not yours. Here are messages to copy, one for each side of the family.

For the centimeter side:

"New mark today! Mila is 103.5 cm (40 3/4 inches). That's 7 cm taller than last March."

For the feet-and-inches side:

"Mila's birthday height: 3 ft 4 3/4 in (103.5 cm). Up 2 3/4 inches this year."

For a guessing game before the photo, again in the reader's unit:

"Guess before you open the photo: how many centimeters has Mila grown since your visit?"

Before each measuring day, run through this short list so the number you send is one you trust:

• ☐  Shoes and thick socks off, hair accessories out
• ☐  Heels, bottom and shoulders against the wall, eyes looking straight ahead
• ☐  A flat book or ruler level on the head to find the line
• ☐  Same time of day as last time, if you can manage it
• ☐  Measured once, in the home unit, by one adult
• ☐  Converted from the original number, then logged with the date written out

Once or twice a year is plenty for most kids. Lining the measuring day up with a regular video call makes it an event for the far-away side of the family too. Our guide to how often to measure your child's height has a cadence by age.

When there are charts in two countries

Some families keep a second chart at the grandparents' home and add a mark on every visit. It works well, with one rule: decide which chart is the official record. The other is the visiting chart, and its marks don't need to match to the millimeter.

They won't match anyway. A different floor, a different measurer and a child fresh off a long flight all nudge the number. Label the visiting chart with the same template and a note such as "at Mamie's house". Nobody will then mistake a visit mark for a missing growth spurt.

A canvas chart is portable, which helps when the second home is a flight away. If you're setting up one for each home, our canvas growth charts are $44 each, and 10% comes off automatically when you buy any two items, which makes a pair $79.20. For more on running the visit itself, see turning grandparent visits into a tradition kids look forward to.

A last note on doctors. Relatives sometimes compare the wall chart with a clinic's numbers or with clinical growth charts. Those are different tools for a different job. For any question about how your child is growing, your pediatrician's measurements are the ones that count.

One mark, two numbers

The whole method fits on a sticky note. Measure once in the unit your chart is printed in. Multiply or divide by 2.54. Write both numbers beside the same line, home unit first, with the month spelled out.

Do that every time, and a grandparent reading in centimeters and an aunt reading in feet and inches are looking at the same child and the same height.

Frequently asked questions