it is best to use an H or I size hook
You can use a bigger hook, or use a thicker thread or yarn. If you know, or can figure out, the multiple of the pattern, you can increase the foundation chain and make it larger in that manner too. If the pattern is completed using squares, you can increase the size of each square or use a joining method that adds width and length to the project. You could also increase the size by adding a multiple round edging around your finished piece.
Your answer depends on the size of the crochet needle you want to use. First, crochet a gauge, so that you have the basic information you need to calculate your raw material requirements.
look at the pattern...... it usually says how much..... i.e.: 5 skeins of yarn As noted above, the pattern generally states how much yarn to use for that pattern. If you are trying to design your own pattern, however, then the process is more complicated. There is no general rule for how much yarn in a pattern, even as to type of pattern, because each is so different. Different scarf patterns, for example, would take different amounts of yarn. Generally speaking, I can probably make a scarf if I have 7 to 10 ounces of yarn. If I am making a hat for a child, I can do it with one 3.5 ounce skein with yarn leftover. For an adult, it depends on the pattern. Sometimes one skein would be enough, sometimes two would be needed. Afghans require more yarn, but amount varies with yarn, hook, and the size of the afghan as well as the pattern. One can take a baby afghan pattern and use chunky yarn to give a larger afghan, but amount of yarn required will be different. If you have a pattern and it gives you the yarn amount in skeins but not ounces, and you want to use a different yarn, then you need to find out how many ounces in that type of yarn, then buy the required ounces in a yarn in the same weight category.
Your answer depends on the gauge that you knit with the yarn and needles that you want to use and the size of the afghan that you want to make.Can you do the math?
The size of the needle depends on the gauge of the pattern you are using. If you are not using a pattern, or are using a pattern that has no gauge, then check the label of the yarn used. Most labels today will give you a size of needle that they recommend for that specific yarn.
that would be a size P crochet hook
You should use a size J/10 crochet hook for a project that requires a 6 mm crochet hook.
The recommended size of crochet hook for working with yarn that is 5mm thick is typically a 5mm crochet hook.
A 00 crochet hook is typically around 9.0 millimeters in size.
For yarn, use an "E" or an "F".
The recommended size of crochet hook in the US for working with a 3mm yarn is typically a size C or D hook.
You should use a crochet hook that is labeled as 5.00 mm for the project.
For this project, you should use a size 6 yarn crochet hook.
Projects that are best suited for a 2.5 mm crochet hook size are typically intricate and delicate items such as lacework, amigurumi, and fine garments like shawls or baby clothes.
To effectively use a 9mm crochet hook in your projects, start by choosing the right yarn weight for the hook size. Maintain consistent tension while crocheting to ensure even stitches. Practice proper hand positioning to avoid strain. Experiment with different stitch patterns to see what works best with the larger hook size.
A 5.0mm would be an H-8 hook.
In UK sizes, a 2mm crochet hook is a 14, it doesn't not have a US size equivalent. Here is a chart with crochet hook conversions from metric to US to UK.