I am a knitting pattern tech editor, I love doing it and I really genuinely like helping designers. It is super exciting to come up with a design that you want to share with other knitters. However, if you want to do that well, in a professional way, then you do need to write a pattern. Often that is the most daunting task. I've decided to start putting out short little posts with a tip or two a time in an attempt to give knitting pattern writers, and particularly those who are newer to the process a bit of a helping hand.
And the more people like it, the more I will do :-)
The first tips I wanted to give this time are with regards to converting between centimetres (cm) and inches (in) (or visa versa). It's a simple thing, but I do get a decent number of questions about this from new designers, and I often find conversion errors when editing patterns.
I generally recommend (when asked) quoting measurements in cm to the nearest 0.5 cm and measurements in inches to the nearest quarter inch. You can chose to be more precise, but in most cases it is hard for someone to actually measure more accurately than that so unless there is a very specific reason for doing otherwise, it is a good rule of thumb.
I highly recommend you use some kind of spreadsheet software when figuring out all the numbers in your pattern. I use Excel (Microsoft Office) but there are other options such as Numbers, from Apple, and Open Office. If people are interested I would be happy to go into spreadsheet use further in the future, but Marnie Maclean has some wonderful tutorials for knitting design on her blog, including several for Excel - do check it out.
When I am converting from cm to in, which is normally how I do things as I work in cm, I multiply the number in cm by 0.394 to give me the number in inches. Then comes the rounding. If one is doing this just for a couple of numbers it is no stretch to round the value in your head. For example:
My measurement is 30 cm
30 x 0.394 = 11.82 inches
This rounds to 11.75 (or 11 3/4) inches
If you were converting from in into cm then you divide your number in inches by 0.394.
But what if you have multiple sizes, or multiple measurements, or even multiple measurements in multiple sizes...? You will waste a lot of time doing this manually. A neat trick for rounding numbers in Excel is to use the "Rounding Function" it already has. This ROUND function is for rounding a number to a certain number of decimal places (which is given by the number you place after the comma). However, it can also be used in the following manner to round to the closest quarter.
Say your unrounded value in inches is in cell D10, you do the following:
This will spit out the value rounded to the closest quarter. What it's doing, for those of you who are interested, is multiplying the number you had in D10 by 4, then rounding this to the nearest whole number, and then dividing it by 4. Broken down for our previous example of 11.82 inches this would be:
11.83 multiplied by 4 = 47.28
47.28 rounded to the closest whole number is 47
47 divided by 4 = 11.75
If you want to round to the closest half, rather than quarter, (like for cm, in the case you started with inch measurements and are converting to cm) then you do:
AND should you wish to round to the nearest eighth it would be:
I use this for all my measurement calculations and I hope that it can help you out too!