The actual calculation of border width in itself is very
basic. However, the number of factors that need to be
taken into account, as enumerated above, are many and
their interrelationship is not as simple. This makes the
determination of border width more of a subjective
process, dominated by intuition rather than by mathematical rigor. For instance, if the available flow rate in
the field supply channel is known, then a first estimate
of the border width can be calculated as the ratio of the
field supply channel discharge to the optimum unit
inlet flow rate. This initial estimate needs to be revised
such that the final border width is an integer divisor of
the field width. Other factors that need to be considered
are width of available farm machinery in relation to
border width and preferred aspect ratio, if any, as
related to adequate spread of water across the border