Now we need to calculate the number of days it takes to travel between two points on our map. The formula is distance divided by speed. First, we need to calculate speed by taking the BMPD and subtracting the amount of time lost by the terrain traveled over. The resulting formula is:
Distance / (BMPD—Terrain Modifier)
For example, traveling by foot is 12 miles per day. According to my chart, if traveling through light forest without a road, we lose 1.8 miles per day, resulting in a speed of 10.2 miles per day. If our map’s scale says that a quarter inch is 20 miles, and our journey is 1 inch, then 20 * 4 is 80 miles. Eighty (80) miles divided by 10.2 miles per day gets our answer: just under 8 days.
80 / (12—1.8)
Calculating speed for every mode of travel, through every type of terrain, for every two locations on our world, can be time consuming. Doing so has an advantage: once the calculations are done, we don’t have to do them again. If we change our mind about scale and have used the provided spreadsheet to track our data, then our calculations will automatically update. This method might be more suited to those intending to use a world over many stories.
By contrast, there is a more manual method, discussed in the next section, that avoids using formulas to change things. Its chief disadvantage is that if we change our mind on scale, calculations we’ve logged before must be redone. Those using a world once or twice might find this is the most suitable approach.
Pre-Set Calculations
The easiest approach to calculating travel between two places is to be generic about it. Looking at the chart below will make the explanation clearer. This chart states in line 1 that everything on it is for traveling on a paved road. Column A shows inches on our map, while columns B and C shows the corresponding number of miles or kilometers; which we use is irrelevant for determining speed. Columns D through J are the number of days to travel each distance from the first three columns by foot, riding horse, etc.
This chart, and others for different terrains, is included in the free template given to newsletter subscribers. The file allows you to change the scale so that .25 inches could be 25 miles instead of 20, for example, and all the chart’s data will change immediately.
Using these pre-set calculations, we never need to use formulas to determine travel time. Instead, we can take our measurement between two places, like Illiandor and Talendor, and see that it is 2 inches. Line 11 above shows us how far that is and how long each travel mode is. And we’re done.
But what if the two inches between these locations are over different terrain? Maybe 1 inch is a road and another inch is rolling hills. We need to grab line 7 from both charts (the line for 1 inch). Now we have realistic data with thought behind it.
In the included template, I’ve added an area for you to add up these values. It looks like this screen shot below. What I did here was take the inches by road and hills and typed them into the chart. Then I add the miles by looking at the other charts. I also added the values for a riding horse, in this case. It shows my final results for a particular journey.
The main problem with the above chart is that our data is not preserved. When we want to do a second journey, we’ll have to replace that data, unless we save it somewhere. Also, if we change our mind about scale, that saved data must be redone. For this reason, some world builders might want to follow the steps in the next section.
Custom Calculations
World builders who intend to use the world for many years to come might want to preserve travel times between many places in a single database. Doing this requires a time investment and familiarity with formulas that will scare away many people. This section is designed for the brave. I did this once for my main world, Llurien, and will likely never do it again, even for new continents, because it’s too much work. There’s also a significant risk of making a formula mistake. A major advantage of doing it is that, once done, it never needs repeating. A change of scale updates the entire spreadsheet.
The details of these custom calculations are discussed in the following template section. Explaining how to do it without the template as a visual guide is unnecessarily challenging. And setting up that template yourself is more pain than you likely want.
