I  am currently agonizing over a few clients who want me to help them plan built-in storage without first plunging into the boxes of books or dishes or keepsakes to determine the final volume of what will be stored. It’s a complete case of the cart before the horse, or more aptly, the cupboard before the tea pot collection.

If you don’t take (literally) measure of your things before building or buying storage, you are doing yourself a huge disservice. Suddenly, you might be stuck with shelves that don’t work for your large art books or holiday platters or the shoe shelves in the closet end up being only half of what is truly needed because the shoes hadn’t been sorted and counted. (One of the morals here is always, always go for adjustable shelving!)

If you have the incredible luxury of being able to have custom-built storage, or even if you are just shopping for containers at IKEA, take the time to inventory the stuff that’s going to be stored — then add 20 percent. Twenty percent is a general rule of thumb for storage, although I think it is a little on the large side, and 10 percent (but no lower) will suffice. This means on a bookshelf, there should be 10 percent of the space left empty for new acquisitions, and when that’s filled, a little pruning must be done. A closet rod should have wiggle room of 10 percent at least, and the same for dresser drawers, a CD cabinet, a pantry, etc.

The 20 percent (or 10 percent) rule could even be applied to time and the calendar. Consider what would happen if you left 10 percent more time in your day between appointments, or 20 percent of your week open to “just be” (or, more often, to allow for unexpected appointments at work and spontaneous meetings with friends). It sounds like an unachievable luxury, but it can be done with a click of the mouse, if you treat your 10-20 percent as sacred space that cannot be scheduled.

Another side to the 20 percent rule has to do with usage of an item. The saying (among organizers) goes, “You use 20 percent of what you have 80 percent of the time.” I know, I know, math is not my strong suit either. What this means is that of all the stuff we have (100 percent), we really use less than a quarter of it the majority of the time.

The best example of this is clothing. Most of us wear the same pieces (jeans, T-shirts, sweaters, workout gear) most of the time. The rest of the closet tends to be the dresses, suits, tuxedos, heels, snow gear and costumes that are pulled out maybe once a year or, even for the more socially active of us, once a month at most.

You can think about this in terms of the kitchen and dining room: how many sets of china do you have, and what dishes do you actually use on a regular basis? In terms of the garage, what tools are used regularly (hammer, screwdriver, pliers) and which are taking up space, rarely used (arc welder, power saw, most of the crescent wrenches). I’m not suggesting anyone get rid of the 80 percent that just sits there waiting to come into play, but I am suggesting that you take notice of it.

For myself, I’m thinking of my snowboard. It’s been about five years since I’ve been on it and it might be time to let it go to someone who would enjoy it while it’s not a complete dinosaur. I have almost zero desire to get back on the slopes. But I have a niece and a couple nephews who love to snowboard, and I might go out with them this year. If I do make the drive to Lake Tahoe, I’d really rather not wait in line at the rental cabin for an uncool board and the equivalent of ski slope bowling shoes. Meanwhile, my snowboard and boots take up little room and are stored properly.

That’s the thought process behind deciding if something you use less than 80-90 percent of the time (or never) should stay or go. I’d say my chances of pulling out my snowboard this year are 10 percent, but by just taking inventory — noticing — I might edge it up to 20 percent or all the way to 100 percent if I actually get out there and have some fun.