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Weak gravitational lensing is one of the most promising tools to investigatethe equation-of-state of dark energy. In order to obtain reliable parameterestimations for current and future experiments, a good theoreticalunderstanding of dark matter clustering is essential. Of particular interest isthe statistical precision to which weak lensing observables, such as cosmicshear correlation functions, can be determined. We construct a fitting formulafor the non-Gaussian part of the covariance of the lensing power spectrum. TheGaussian contribution to the covariance, which is proportional to the lensingpower spectrum squared, and optionally shape noise can be included easily byadding their contributions. Starting from a canonical estimator for thedimensionless lensing power spectrum, we model first the covariance in the halomodel approach including all four halo terms for one fiducial cosmology andthen fit two polynomials to the expression found. On large scales, we use afirst-order polynomial in the wave-numbers and dimensionless power spectra thatgoes asymptotically towards $1.1 C_{pt}$ for $\ell \to 0$, i.e., the result forthe non-Gaussian part of the covariance using tree-level perturbation theory.On the other hand, for small scales we employ a second-order polynomial in thedimensionless power spectra for the fit. We obtain a fitting formula for thenon-Gaussian contribution of the convergence power spectrum covariance that isaccurate to 10% for the off-diagonal elements, and to 5% for the diagonalelements, in the range $50 \lesssim \ell \lesssim 5000$ and can be used forsingle source redshifts $z_{s} \in [0.5,2.0]$ in WMAP5-like cosmologies.

A fitting formula for the non-Gaussian contribution to the lensing power spectrum covariance