Having said that there will be times when you will want to do a ‘back of an envelope’ type of estimate perhaps to compare quickly two pieces of business and so it is useful to have a fairly accurate idea of major world maritime distances, from which basis one can usually estimate cross voyages. Perhaps the best method is to divide the world into areas (somewhat naturally this tends to fall into oceans) and then learn and remember a number of strategic mileages across each area. There is a division of thought on whether one should learn actual distances or think in terms of days ‘steamed’ but, since most professionals tend to think in terms of days, the latter is perhaps the more favourable alternative. As a guide, a speed of 14 knots works out almost exactly 3 days per 1000 nautical miles (i.e. 14 knots x 24 hours x 3 = 1008 nm) and, on this basis, it is relatively easy to remember that, for example, a transatlantic voyage between the US Gulf (say New Orleans) and Rotterdam takes 15 days in good weather, whilst that between USNH (United States, North of Cape Hatteras) – say Hampton Roads – and Rotterdam, lasts for 11 days in good weather. Under this relatively simple system, representative voyages can be calculated and memorised. Provided you remember to correct the time allowed in accordance with various speeds, this should make the task much easier than otherwise might be the case. Having established a method of calculating the length of a sea-passage, we can next consider the basic elements of a voyage estimate and produce a ‘skeleton’ on which to hang the ‘flesh’ of any particular calculation. But before we start on examining the make-up of an estimate it is as well to determine just how it will be produced.