How to Calculate How Much Paint You'll Need

April 1, 2025

The Simple Formula to Figure Out How Much Painting You'll Actually Need

Ever stood in the paint aisle, staring at a sea of colour cards, wondering not just what shade you're painting your living room... but how many tins you actually need?

You’re not alone. So many folks walk through the doors at our Strathalbyn H Hardware Paint Shop excited to get started, but with one big question burning in their minds: “How much paint do I need?”

If you’ve ever overestimated and ended up storing half-full tins like your garage is a mini Bunnings, or worse—underestimated and had to stop mid-wall for another can—this guide is just for you. And don't worry, I’m going to make it super simple.

Let’s Talk Square Metres, Not Guesswork

Before we get to the good stuff like tint selection or finishes, you’ve got to know how much space you’re working with. Grab a tape measure, a pen, and a piece of paper—or let's be honest, probably your phone Notes app.

Step 1: Measure the width and height of each wall. Multiply them to get the area of each wall. Then add up the area for all the walls you’re painting.
Step 2: Subtract the space taken up by windows and doors. Standard doors usually take up about 1.8m² and windows about 1.5m² each.
Step 3: Multiply by the number of coats you plan to apply. Trust me on this, one coat is rarely enough for a rich, even finish—especially if you're switching from a dark to a light colour.

So it might look something like this:

4 walls at 3m wide and 2.4m high = 4 x (3m x 2.4m) = 28.8m² Fresh total: 28.8m² – 3.3m² (1 door + 1 window) = 25.5m² Times 2 coats = 51m² to cover.

Okay Cool. But How Much Paint Covers How Much Space?

On average, 1 litre of quality paint covers around 12 to 16m² per coat. So for that 51m² we calculated earlier, you’ll need about 3.5 to 4.5 litres.

Keep in mind that coverage can sway depending on whether your surface is smooth or rough, new or previously painted, light or dark. Bare timber or plaster will soak up more paint than sealed surfaces.

Choosing the Right Paint Matters (a LOT!)

If you're still deciding what kind of paint to use, you want something that glides on like smooth butter and holds colour beautifully year after year. That’s where Haymes Paint hits the mark. Their Expression Low Sheen walls paint is an absolute gem. It’s got durability, washability, and that soft finish we all love for living rooms, bedrooms, and hallways.

For doors and trims? You might love Haymes Expression Gloss or Semi Gloss finishes equally. Once you've done your maths, bring those numbers in-store and we’ll help you pick the right can size. For example, if you’ve got to paint 50m², a 4-litre tin will get you close—add a 2-litre backup if it’s a trickier surface or doing bold colours.

Pro-Tips to Avoid Paint Panic

Always round up. Between spillage, substrate absorption, and touch-ups later—it's always better to have a little more than not enough.
Use a primer for seal and better coverage. Especially for previously unpainted surfaces or massive colour changes. Haymes Ultra Premium Prepcoat is a lifesaver for that.
Don't forget ceilings! Most of us fixate on what’s directly in front of us but forget the overhead canvas. Chances are, it needs love too.

Using Online Calculators (And When to Ignore Them)

Sure, a quick Google will suggest paint calculators for “fast estimates,” but I’ve always found they work best only when you feed them very accurate inputs. If you’re guessing measurements, or unsure about coat counts and surface type, you're better off stopping by at the shop. We can walk through your project with you and work it out together.

Still Feeling Unsure?

Listen, this is your home. It’s not just about slapping colour on walls—it’s about creating a space that feels right. Whether you’re freshening up the bedroom or going bold in the kitchen, the last thing you want is to pause halfway through and wait for more paint to settle in. That lilac wall isn’t going to paint itself, is it?

Pop in to see us at 37 East Terrace for an in-person chat. We’ll measure out with you, recommend what you’ll need down to the last drop, and even match that mystery shade from your Pinterest screenshot. No assumptions. Just honest, tailored advice.

Bring your vision. We’ll bring the know-how, and the Haymes Paint that'll turn your next room refresh into something you can brag about at the next barbecue 🤩

Happy painting,
Candeece 🎨💖