The paper introduces a computable measure of entanglement for mixed states of bipartite systems, which is based on the trace norm of the partial transpose of the density matrix. This measure, known as the *negativity* $\mathcal{N}(\rho)$, is shown to be an entanglement monotone, meaning it does not increase under local operations. The negativity is used to bound the teleportation capacity and the distillable entanglement of mixed states. The paper also discusses the *logarithmic negativity* $E_N(\rho)$, which is an additive quantity and provides bounds on the distillable entanglement. These measures are applied to derive explicit expressions for pure states, symmetric mixed states, and Gaussian states of light fields. Additionally, the paper explores the extension of these measures to multipartite systems, providing a set of computable parameters to quantify multipartite entanglement.The paper introduces a computable measure of entanglement for mixed states of bipartite systems, which is based on the trace norm of the partial transpose of the density matrix. This measure, known as the *negativity* $\mathcal{N}(\rho)$, is shown to be an entanglement monotone, meaning it does not increase under local operations. The negativity is used to bound the teleportation capacity and the distillable entanglement of mixed states. The paper also discusses the *logarithmic negativity* $E_N(\rho)$, which is an additive quantity and provides bounds on the distillable entanglement. These measures are applied to derive explicit expressions for pure states, symmetric mixed states, and Gaussian states of light fields. Additionally, the paper explores the extension of these measures to multipartite systems, providing a set of computable parameters to quantify multipartite entanglement.