Should you paint the ceiling the same colour as the walls?

Here are the two ceilings in a room we designed with real IKEA and B&Q products, so you can compare them rather than take our word for it.

What does a painted ceiling look like in a bedroom?

This is a Japandi bedroom we designed: warm taupe walls in Dulux Heritage Mid Umber Velvet matt (B&Q, £49 for 2.5L), a dark brown IKEA IDANÄS storage bed (£499), an IKEA PAX wardrobe (£381), a LOHALS jute rug (£179) and a plain white GoodHome Klentony pendant (£15). The whole room came to £1,625.96 for 13 products.

Both pictures show the room from the doorway, low enough that a good stretch of ceiling is in view. In the first, the ceiling is plain white.

The walls are a warm, mid-dark taupe and the ceiling is a cool white, so there's a clear line where they meet and your eye goes straight to it. The room feels like a coloured box with a bright lid.

In the second, the walls haven't changed. The ceiling is a lighter, warmer shade of the wall colour, a pale blush-taupe in this picture.

The line along the top of the walls has gone soft, the pendant stands out less against a white surface, and the room feels more enclosed and calmer. It's also slightly darker overhead, which is the trade-off, and in a bedroom you mostly use in the evening it's the one we'd choose.

Should the ceiling be the same colour as the walls?

It can be, and in a bedroom it often looks good. Farrow & Ball says the same colour on walls and ceiling is soothing and looks more subtle than you'd expect, with no sharp lines. Escapology adds that the uniform colour hides flaws.

The same sources are honest about the downsides. Escapology says it can make a big room feel cavernous and suggests it suits small and medium rooms, and Fantastic Handyman points out that it can hide features like coving and takes a lot more paint.

The ceiling in the second picture is a shade lighter than the walls rather than identical, for one reason. A ceiling in exactly the wall colour sits in shadow more than the walls do, because the light comes from the window and the ceiling gets it second-hand, and a lighter tone evens that out. The pictures only show the lighter version, so treat that as our judgement rather than a measured result.

How do you get a lighter shade of the wall colour?

Farrow & Ball describes the old decorators' trick: mix about 25 per cent of the wall colour into the ceiling white. It's cheap, it gives a ceiling that matches the walls in character, and you can do it with whatever's left in the tin.

Two practical points. Mix all the ceiling's paint in one container so the colour doesn't drift between batches. And check what your wall paint is: B&Q sells the Mid Umber in this room as a "wall paint", not a "wall & ceiling" emulsion, so read the tin before you use it on a ceiling, or tint a white that's sold for ceilings instead.

Do dark or coloured ceilings make a room smaller?

Sources disagree here. Dulux says a bright white ceiling can make a room look bigger than it is, and recommends it for low ceilings. Farrow & Ball says almost the opposite: a bright white ceiling can make the room feel darker through contrast, while a darker ceiling in a tall room visually lowers it and makes it more intimate.

My Bespoke Room lands in between: dark ceilings work best in rooms with generous proportions, and for lower ones it suggests softer greys and muted pastels over deep shades. Clare suggests a step lighter or darker than the walls for subtle contrast.

In a normal-height bedroom like this one we'd stay in the pale, close-to-the-walls range, and go properly dark only in a room where the ceiling is visibly high and you'd like it to come down.

What finish should a painted ceiling be?

Matt, in most rooms. Dulux recommends matt, silk or soft sheen formulas and says the best ceiling paint is flat and doesn't reflect light, and My Bespoke Room says the same for dark ceilings, to stop glare from the lights. Farrow & Ball goes the other way and describes full gloss ceilings as glamorous, because they bounce light around a gloomy room. That's a bolder look and shows every dip in the plaster, so we'd save it for a ceiling in good condition.

The walls here are a velvet matt, so a matt ceiling matches them.

What did it cost, and what would the other options have cost?

The room's own paint is the wall colour, so these ceiling prices are B&Q's and aren't part of the £1,625.96. All are for 2.5L.

• White ceiling: Dulux Pure Brilliant White matt wall & ceiling emulsion, £20 (5L is £25)
• Lighter wall colour, mixed at home: that same £20 white plus some of the wall paint you've already bought
• Ready-tinted: a Dulux Easycare coloured wall & ceiling emulsion, £32
• Same colour as the walls: another tin of the £49 Mid Umber, if it's suitable for ceilings

So the lighter ceiling, mixed at home, costs about the same as a plain white one, and the ready-tinted version is £12 more, which is under 1% of the room's £1,625.96. The cost of the same-colour option depends on how much paint your ceiling needs, and we haven't worked that out for this room. The coverage per litre is on the tin, so check it against your ceiling's area before you buy.

How do you check the colour before you paint?

You'll be looking at a ceiling from underneath and at an angle, so a swatch held up against the wall tells you less than you'd think.

1. Mix a small amount of your lighter shade, using the 25% mix, in a clean pot.
2. Paint it on a large sheet of lining paper or card, an A3 sheet or bigger.
3. Tape it to the ceiling and look at it from the bed, in the evening with the lights on as well as by day.
4. Compare it with the wall colour next to it, not with a white ceiling in your head.

If it looks nearly the same as the white, add more wall colour. If it looks as dark as the walls, you've gone too far for a lighter ceiling, though that may be the effect you want.