This is another  one of those awful questions which is most efficiently answered by “That’s entirely dependent on you and your individual tastes and style”.
But, as I’ve already mentioned, I rather hate that kind of answer. So I’m going to actually discuss some of the factors that affect this, and hopefully I’ll be able to provide some food for thought and actually help you make some informed choices about how long your rope lengths are, how many of them you have, etc.

I’m going to discuss
– the typical lengths of rope, and why
– the number of lengths of rope, and why
– and other important bits and bobs that it’s very handy to have in your rope kit.

Fact One: The typical length for shibari style rope is either 7 or 8 metres long.

That’s not arbitrary. There are actually reasons for this.
One: When you’re doing shibari, your rope is doubled. This makes for more efficient tying (which is awesome), and it halves the length of your rope.

The usefulness here is that now you have a very manageable length of rope. You can do quite a lot with it (for example a comfortable wrist tie that is also tied off to the bed, start a harness, etc) but the trailing ends aren’t so long that you spend forever pulling it through each individual knot and turn.
It also means you’re not constantly tripping over the  ends or standing on your rope, and neither is the person you’re tying. It may still happen, but it won’t happen as much as if you had an enormous 15 metre length or something.

So you’ll have a few lengths of 7 – 8 metres, which can be joined together as need be.

However, if you’re smart, you’ll also have a few shorter lengths.
There may be times when you want to just do a wrist tie, or an ankle tie, and you don’t want to have lots of leftover rope. So bringing the size down for about 4 lengths of rope can be really helpful (think a person with their wrists and ankles tied apart on a bed, sort of spread eagled).
The other advantage to having a few shorter lengths in your kit is that often, you’ll have just NEARLY enough rope to finish your tie, but not quite. And you  don’t want to add a another whole 7-8 metres, because then you have to figure out what to do with all the rest of it!

(This is when I absolutely delight in having shorter lengths of rope as part of my kit.  I use about 3.5 metres for my shorter lengths; it works well. )

How many lengths overall in your kit is an interesting question.

Two – three lengths is the average amount of rope it takes to do a shibari closed-leg tie, such as a futomomo. Factors which change this include how many wraps you want to use in order to make it comfortable or supportive, and also the size of the leg that you’re tying.

A chest harness, depending on how elaborate it is, the width of the supporting wraps (double or triple, etc) and the size of the person you’re tying, is likely to be somewhere between 2-4 lengths of rope.

So let’s assume you want to have enough lengths for most situations where you want to tie one person.

One harness; let’s max it; 4 lengths of rope
Plus leg ties for more restraint and immobility; again maxing it for both legs:
6 lengths of rope.

Okay, so let’s make that roughly 10 lengths of rope. This is seriously maxing out over and above most required amounts. I mean, that’s a freaking suspension kit right there.

However, that recipe is how I work out how much rope to have in my kit. I think about who I’m going to be tying; the number of lengths going into the ties, and the  ties I’ll use; and then I’ll generally add a spare length plus some short bits. Plans may change; they frequently do. And short bits are always useful to have.

When I designed my  last two rope sets, I opted for 10 longer lengths + 4 shorter lengths in each.

I’ve never been caught short of rope since.
(Though I tend to leave some of the longer lengths  at  home when I travel to parties, otherwise I’d never fit everything into my toy bag!).

Speaking of which, rope isn’t the only thing that’s useful to have in your rope kit.

I generally also have:

– EMT Shears; Highly recommended. Never leave home without them. You can use other cutters, but EMT shears are the standard due to safety factors; Raptor EMT Shears are probably the best ones around, but are also pricier.

– A blindfold; whether a piece of cloth, a sleeping mask, or a nifty adjustable leather or steel thing, a blindfold is very very useful in lots of situations. (Some people  like to wrap their pile of rope in a cloth bundle; this works well to stop  the rope from picking up dust and bits and pieces, but in a bedroom situation also gives you another blindfold option).

– A pack of hair ties (because I generally don’t want loose hair getting caught  in the rope).

– Back up cutter (never had to use it, but you never know) I have a curved Karambit knife. Again, designed for safety due to curved blunt spine.

– Varied sensation and/or impact toys. Because when you have someone tied up  and blindfolded it’s often a lot of fun to add in other sensations.

– If I’m doing suspension stuff, I’ll generally have a few bits of gear that relate to that as well.

– (If I had a medical condition I would include meds; If I ever develop one, you can bet your ass those will be present)

– Condoms! Because safe sex is a wonderful thing.

I tend to deliberately limit how much I bring to what will fit in a single duffel bag, because I like to challenge my creativity a bit. It’s not about how  many toys I have, or how much rope (though I hate falling short), it’s about me and the other person and the fun things I can think of.

What you’ll want in your own rope kit will be heavily dependent on how you play; so think about what you’re likely to want to do, and add what you need to your rope kit so you know you have it ready. It’s all about your style.

The main idea with this post is to demonstrate the kind of rationale you might have in planning your rope kit; that’s the part I hope you find useful.

Happy tying!