What are realistic emissions targets for the world's six largest emitters that sum up to Paris-compatible emissions? To answer this question, this paper varies key framework data on the available global CO2 budget and the sharing mechanism to calculate top-down national emissions targets using the Extended Smooth Pathway Model (ESPM). The Paris Ambition Mechanism is based on a bottom-up approach. However, if the national targets are not Paris-compatible in sum, the question arises whether national targets represent an adequate contribution to the necessary global efforts. An open and transparent discussion of this issue can contribute to NDCs that are Paris-compatible in sum. Here is a simplified web app to reproduce the results: http://national-budgets.climate-calculator.info