JSFiddle - React, Tailwind, and code Playground

HTML

<div align="center">
	<table width="1260">
		<tr>
			<td>
				<form>
					<p>
						<table width="100%" border="0" cellspacing="0" cellpading="0">
		  					<tr>
								<td width="1%"  bgcolor="#000000">&nbsp;&nbsp;&nbsp;&nbsp;</td>
							</tr>
		  					<tr>
								<td width="1%"  bgcolor="#000000">
									<h2>
										<a href="http://www.olipo.com.br/">
											<img src="logo.png" width="192" height="137" />
										</a>
									</h2>
								</td>
								<td width="1%"  bgcolor="#000000">&nbsp;&nbsp;&nbsp;&nbsp;</td>
		  						<td width="99%" valign="middle" align="center" bgcolor="#F58634">
									<font color="#ffffff" face="Arial, Helvetica, sans-serif" size="+3">
										<strong>INDICE DE FORÇA MUSCULAR RELATIVA</strong>
									</font>
								</td>
		  					</tr>
						</table>
					</p>
					<p>
						<table width="100%" border="1" cellspacing="0" cellpading="5" class="StackTable">
							<tr>
								<td width="22%">
									<input name="pesoaluno" type="text" size="2" /> Peso Al. Kg
									<br>
									<input name="WeightLifted" type="text" size="2" /> Peso Tes. Kg
									<br>
									<input name="RepsPerformed" type="text" size="2" /> Repetições
									<br>
									<input type="button" value="Calcular" onclick="calc(this.form)" />
									<input type="reset" value="Resetar" name="Reset" />
								</td>
								<td width="2%" align="center" bgcolor="#B09E66">
									<input id="ifrm" name="ifrm" TYPE="text" SIZE="2" />
									<br>IFRM.
								</td>
								<td width="2%" bgcolor="#FF6600">
									<input name="A1" type="text" size="5" /> 40%
								</td>
								<td width="2%"  bgcolor="#33CCFF">
									<input name="A2" type="text" size="2" /> 45%
								</td>
								<td width="2%"  bgcolor="#FFCC00">
									<input name="A" type="text" size="2" /> 50%
								</td>
								<td width="2%"  bgcolor="#00CC33">
									<input name="B" type="text" size="2" /> 55%
								</td>
								<td width="2%" ...

JavaScript

function calc(form) {
	if (form.RepsPerformed.value < 10) {
		form.OneRepMax.value = Math.round(form.WeightLifted.value / (1.0278 - 0.0278 * form.RepsPerformed.value));
	} else if (form.RepsPerformed.value == 10) {
		form.OneRepMax.value = Math.round(form.WeightLifted.value/0.75)
	} else if (form.RepsPerformed.value > 10) {
		alert("Reps Performed must be between 1 and 10");
		return;
	}

	form.ifrm.value = (form.OneRepMax.value / form.pesoaluno.value);

	form.A1.value = Math.round(form.OneRepMax.value * 0.40);
	form.A2.value = Math.round(form.OneRepMax.value * 0.45);

	form.A.value = Math.round(form.OneRepMax.value * 0.50);
	form.B.value = Math.round(form.OneRepMax.value * 0.55);
	form.C.value = Math.round(form.OneRepMax.value * 0.60);
	form.D.value = Math.round(form.OneRepMax.value * 0.65);
	form.E.value = Math.round(form.OneRepMax.value * 0.70);
	form.F.value = Math.round(form.OneRepMax.value * 0.75);
	form.G.value = Math.round(form.OneRepMax.value * 0.80);
	form.H.value = Math.round(form.OneRepMax.value * 0.85);
	form.I.value = Math.round(form.OneRepMax.value * 0.90);
	form.J.value = Math.round(form.OneRepMax.value * 0.95);
}