Walking accessibility gains significant attention in recent years in urban planning. Various software tools provide accessibility analysis based on network graphs. However, the slope component is often overlooked. This paper introduces an open-source QGIS plugin which automates calculation of isochrones and an Accessibility Index, inspired by the 15-min city concept. The Accessibility Index evaluates access to various services within predefined distance ranges, weighted by service importance. Four computational methods are available: buffer analysis, network analysis and slope-adjusted network analysis using Tobler’s hiking function and the Naismith-Langmuir rule. The QGIS plugin allows straightforward implementation and a high level of reproducibility, resulting in optimized computing time and resources. The tools Average altitude of point features, Slope calculation of network segments, Split network with points, and Accessibility Index can be used together or separately for the assessment of the urban environment. The calculations showed a significant decrease in Accessibility Index in the case of hilly terrain compared to the typical network analysis without considering the slope.