  We present an experimental approach using magnetic force microscopy for
measurements of the absolute value of the magnetic penetration depth $\lambda$
in superconductors. $\lambda$ is obtained in a simple and robust way without
introducing any tip modeling procedure via direct comparison of the Meissner
response curves for a material of interest to those measured on a reference
sample. Using a well-characterized Nb film as a reference, we determine the
absolute value of $\lambda$ in a Ba(Fe$_{0.92}$Co$_{0.08}$)$_{2}$As$_{2}$
single crystal and a MgB$_2$ thin film through a comparative experiment. Our
apparatus features simultaneous loading of multiple samples, and allows
straightforward measurement of the absolute value of $\lambda$ in
superconducting thin film or single crystal samples.
