bpm : <input type="text" id="bpm"><br>
<input type="button" onclick="go();" value="convert!">
<br>
<br>

<div id="normal"></div>





<script>
function go(){
    var bpm = document.getElementById('bpm').value;


    var normal = bpm*1;

    document.getElementById('normal').innerHTML = "recommended AR: <b>"+toAR(normal)+"</b>";

    function toAR(bpm){

        // get the time between tics using bpm
        var msbpm = ((1/(bpm/60))*1.5)*1000;

        //transform to AR
        var ar = Math.round(100 *(
            (-0.00666*msbpm)+12.65)
        )/100;

        if (ar > 10) {
            ar += " ( not supported by osu ! )";
        }
        return ar;
    }

}
</script>