In order to identify taro horticultural varieties, some calculations of the dimensions of the leaf blade (lau) and petiole (ha) may need to be made. For this, a ruler and a calculator are needed.
Four measurements of a mature, fully expanded leaf blade are needed:
| Total leaf length | Length from the tip to the sinus cut | Length from the tip to the piko | Maximum blade width |
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Two measurements of the petiole (hā) are needed:
| Total petiole length from the top of the corm to the attachment of the blade | The length of the sheath, from the top of the corm to the top of the sheath split |
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Using a calculator, the four ratios can be calculated as follows:
| Divide the total length by the maximum width | Divide the length from the blade tip to the base of the sinus cut by the total length | Divide the length from the blade tip to the piko by the total length | Divide the length of the cut in the petiole by the total petiole length |
 Ratio: total length to maximum width |
 Ratio: length-to-sinus to total length |
 Ratio: length-to-piko to total length |
 Ratio: sheath length to total length |
These numbers can then be entered into the key:
