BTU Explained : How to calculate the BTU for a room

That is, BTU to you and me. If you’re wondering what on earth this means, well, you’re going to have to cast your memory back to your glory days of school.

Simply put, 1 BTU is equal to 1055 Joules. The “joule” is a unit of energy that forms part of the International System of Units. It is similar to the energy transferred to an object when a force of one newton acts on that object in the direction of the force’s motion through a distance of one meter.  OK, so you didn’t really have to know what all of that is, but that’s kind of the point of this post.  We’re going to break all of this down for you, so you know how it’s relevant to planning your bathroom and accessories. (That’s all the clever speak you’re going to get from us).

All you need to know is this: we’re going to take all of the guesswork out of it for you and leave you with a bathroom that is warm, enticing, and a space you’ll never want to leave.

How many BTU do I need in a bathroom?

So you’re thinking about turning your current bathroom into the bathroom you’ve always wanted. To do that, you’ll need to know a few things first, and this “BTU” business is a part of that. When installing a radiator, size does matter.  Too small, and it’s like it’s not even there, too big, and you’re in a sauna - not the good kind.

But luckily for you, we have a BTU calculator that’s going to make all of that as easy as, well, taking a bath.

It is a good idea to get this done right, though, especially if you’re planning a general overhaul of your bathroom because whether or not you’re installing a shower, towel rack, or putting in a free-standing bath, all of these factors will have an impact on how much “space” you need to be heated.  There is nothing worse than getting out of a hot bath or shower into a bathroom that’s less than comfortable - and we hate to break it to you, but winter is just around the corner.

How do I work out what size radiator I need for my bathroom?

Well, that’s where those BTU calculations come in very handy, and if you use the BTU calculator that we’ve already created, this will take all the guesswork out of it.

In most cases, one or two radiators will more than suffice, but if you’re blessed with a more oversized bathroom, or perhaps one that opens directly into a bedroom or walk-through closet - then you’re going to need more. 

The amount of BTU’s required per radiator will depend on the amount you have in the room. You have to divide the total BTU requirements by the total number of radiators in the room, which will calculate the average BTU required per radiator.

But again, don’t get caught in the details - that’s what we’re here for.

What is a suitable BTU for a towel rail?

Who doesn’t love a heated towel rail, right?

But, you do want to make sure that you’re providing sufficient heat, and assuming that the towel rail will be the only source of heat in the bath or shower room, the general idea is to have 400 BTUs per square meter of floor space, but, this does depend on the design and style of the bathroom: walls, windows, and overall spatial reasoning.

OK but, how does this BTU make a difference to a heating plan?

Well, it doesn’t just make a difference to a heating plan. It also makes a difference to planning for air conditioning, but since we’re focusing on radiators here, let’s explain.

Remember at the start of this section that BTU stands for “British Thermal Unit.”

So here’s how it works: One BTU refers to the amount of energy required to increase the temperature of a pound of water by 1degree Fahrenheit. So when you factor in the size, shape, and design of your bathroom, you’ll figure out how many BTUs you’re going to need to heat your space and how many radiators or towel racks will accomplish that.

Any questions? We hope so.

Renovating your bathroom, much like any space in your home, is not a project one takes on lightly; what may seem obvious to some is a complete anomaly to others, but that’s why we’re there. We’re here to ensure that you get expert, honest, and practical advice so that you’re neither over-sold nor under-supplied.

Call us today on 028 9077 0188 to see why Trustpilot rates us so highly and how to make all the difference for you.