What is ”size” in Esperanto?

Question

I can tell the difference betweeen a quantity and the presence of a quality.

• rapido - speed / rapideco - quickness
• longo - length / longeco - longness
• pezo - weight / pezeco - heaviness

I thought the same followed for grand-. Then, the correct word for size would be grando. But grando refers to all of the words on the left side above. It means physical quantity. How do I say size then? I searched both PIV and reta-vortaro and found no entry with a definitiom which matches what I am looking for.

Mi volas aĉeti ĉi tiun ĉemizon, sed mi ne trovas mian grandecon.

Is this sentence correct?

Answer 1

According to several non-English translations in ReVo grando means both magnitude and size.

Here are some examples from the Spanish-Esperanto Dictionary by F. de Diego:

Kiun grandon havas la ŝuoj? [What size are the shoes?]

Mi portas la grandon 43an [I wear size 43 (shoe size)]

I suppose the sentence [...] mi ne trovas mian grandecon is correct.

Answer 2

As you clarified the system yourself, the correct pair is

• grando - size / grandeco - bigness

If you don't want to express that your shirt is big, but that it has the right size, your sentence should be

Mi volas aĉeti ĉi tiun ĉemizon, sed mi ne trovas mian grandon.

Cf. the following quotes from the Tekstaro, where grando means "size":

• la okulo erare mezuris la grandon de l’ objektoj
• La kuirilo troviĝis en kvar grandoj
• mi finis la mezuradon kaj kalkulojn pri la grando de la tero