# The unit of energy, 1 dm³ atm, is equal to how many calories?

I surfed through the internet and visited a number of chemistry websites but only in vain. I couldn't find an answer.

$1\ \mathrm{dm^3} = 1\times 10^{-3}\ \mathrm{m}^3$
$1\ \mathrm{atm = 1013.25\ mbar = 101.325 kPa = 101325\ {kg}\cdot{}m^{-1}\cdot s^{-2}}$
$1\ \mathrm{atm \cdot dm^3} = 1\times 10^{-3}\cdot 101325\ \mathrm{m^3 \cdot kg \cdot{}m^{-1}\cdot s^{-2}} = 101.325\ \mathrm{kg \cdot{}m^{2}\cdot s^{-2}}$
$1\ \mathrm{atm \cdot dm^3 = 101.325\ J = 101.325\cdot 0.2390\ cal= 24.217\ cal}$
General Gas Constant, $\mathcal{R} = 0.0821\:\mathrm{dm^3\cdot atm\cdot K^{-1} mol^{-1}}$
General Gas Constant, $\mathcal{R} = 1.989\:\mathrm{cal\cdot K^{-1} mol^{-1}}$