documentclass[tikz,border=1cm]{standalone}

usepackage{printlen}
uselengthunit{cm}
newlength{tmpdim}

begin{document}
begin{tikzpicture}[x=1cm,y=1cm]
    draw[line width=1pt] (0,0) grid (8,3);

    deflastx{(0,2)}
    defvertA{(1,2),(2,2),(3,2),(4,2),(5,2)}

    foreach x [count=xi from 2,remember=x as lastx, evaluate=x as n1 using {veclen(lastx,x)}] in vertA {
        draw[blue, line width=2pt] lastx -- x node [midway,above] {n1};
        fill[red] x circle (0.1);
        node[red,below] at x {xi};
}
end{tikzpicture}

end{document}