How is the area unit “m²” pronounced?

Question

In the sentence below:

Das Zimmer ist 14 m² groß.

How the m² is read?

I know in English you say square meter.

Answer 1

The superindex ² is pronounced quadrat. In combination with meters, you say:

Quadratmeter (engl. square meter[s])

The action to take the square of a quantity is

quadrieren

There's an irregular power left (in the sense that it has its own name, instead of just saying hoch N), namely three:

Kubikmeter

There also exists the slightly more technical quartisch for the fourth power, e.g.:

quartisches Potential

In the context of polynomials, the forth power is also biquadratisch.

Answer 2

As was already said, the best way — and the only way for room dimensions — to read m² would be

Quadratmeter

However, that doesn’t work that well with all units. Everything that relates to area, i. e. the different metres, and the old imperial units like Elle or Fuß, will work. For most other units, it’s slightly preferred to say something like

Beschleunigung misst man in Meter durch Sekunde zum Quadrat.

or shortened informally to

[…] Meter durch Sekunde-Quadrat.

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This is also the way, variables in mathematical equations are treated. So if your m² isn’t the unit for the area of a room, but actually mass squared in some formula, you would say

m-Quadrat.

Answer 3

In addition to c.p.s answer, some more units:

• m² and m³
  • 14 m² = vierzehn Quatratmeter
  • 3,18 m³ = drei Komma eins acht Kubikmeter
  • 3,18 m³ = drei Komma achtzehn Kubikmeter (only if there are exactly 2 digits after the comma)
• % (technically it's just a pseudo-unit, but as matter of Language it is a unit)
  • 0,5 % = null Komma fünf Prozent
  • 0,5 % = ein halbes Prozent
  • 1,25 % = eins Komma fünfundzwanzig Prozent
  • 1,25 % = ein-einviertel Prozent (only when talking of interest in an economic context, and only if the fraction is a multiple of 1/4 or 1/8)
  • 1,375 % = eins Komma drei sieben fünf Prozent (not: ... Komma dreihundertfünfundsiebzig ...)
  • 1,375 % = ein-dreiachtel Prozent (as described above)
• km/h
  • 130 km/h = hundertdreißig ka-em-ha (colloquial and well-understood, but technically wrong because the fact, that the hour is a fraction, is ignored)
  • 130 km/h = hundertdreißig Stundenkilometer (colloquial and well-understood, but technically wrong)
  • 130 km/h = hundertdreißig Kilometer pro Stunde (technically correct, but rarely used)
• €
  • 7,80 € = sieben Komma achtzig Euro (absolutely correct and also well-understood, but the next version is used much more often)
  • 7,80 € = sieben Euro achtzig (only currency-units can replace the word Komma)
  • 12,56 €/m² = zwölf Euro sechsundfünfzig pro Quadratmeter
• other squares and cubes
  • 9,81 m/s² = neun Komma einundachtzig Meter pro Sekunden-Quadrat
  • 12.000 kg*m/s² = zwölftausend Kilogramm Meter pro Sekunden-Quadrat
  • 7874 kg/m³ = siebentausendachthundertvierundsiebzig Kilogramm pro Kubikmeter