<p>In this study, solutions were derived to calculate the two horizontal components of gravity anomaly vectors using a horizontal polygonal thin plate. Although analytical solutions for the three components of the gravity anomaly vector for a rectangular prism model have been derived, it is sometimes difficult or inefficient to approximate subsurface structures by assembling rectangular prisms. An alternative to these models is to approximate an arbitrary three-dimensional subsurface structure by stacking several polygonal thin plates. As the solutions presented here are approximate, comparative analyses with analytical solutions and higher-accuracy numerical solutions were conducted for the rectangular prism Δ<i>g</i>_<i>x</i> and Δ<i>g</i>_<i>y</i>, and for the model assuming practical field modeling. The results showed that by setting a small thickness Δ<i>z</i> for the horizontal polygonal thin plate, a solution comparable to the analytical or correct solution can be obtained. For a realistic analysis, setting Δ<i>z</i> to match the measurement accuracy of Δ<i>g</i>_<i>x</i> and Δ<i>g</i>_<i>y</i>, or the conversion accuracy from Δ<i>g</i>_<i>z</i> to Δ<i>g</i>_<i>x</i> and Δ<i>g</i>_<i>y</i>, will enable practical numerical solutions to be obtained.</p> Graphical Abstract <p></p>