Luggage space – What's the difference?

Ever wonder why the brochure for Ford's now-defunct Territory lists its luggage capacity at 1153 litres, but for BMW's dimensionally similar X5 the boot space ranges from 650 litres right up to 1870?

In a nutshell, the answer is this: Ford uses a different means of measuring the luggage capacity – one that allows for goods stacked all the way up to the headlining behind the second-row seat.

By contrast, the X5's figures use a different method of measurement – a different standard – for calculating available boot space. The 650-litre figure is based on the volume up to the top of the rear seat only, not all the way to the headlining. That's why it's only about 56 per cent of the Territory's. But BMW also publishes the 1870-litre figure for consumers who want to know how much the X5 will carry by volume, if all the seats are lowered and the vehicle is filled to its absolute maximum.

For families in particular, discrepancies like these could lead to an ill-considered purchase. If that planned purchase won't accommodate the children's stroller, Dad's golf clubs, the kids' bikes or even the weekly shopping, it's important to know. Luckily, details on the amount of luggage space in a particular vehicle model are usually available from technical specification pages in brochures or on websites.

Some manufacturers give the basic dimensions of the luggage space in length, width and height, which is pretty handy, but most don’t. Nearly all manufacturers will however quote a luggage compartment volume in litres.

OK, so regardless of whether a number of litres really gives us a sense of what we can fit in the boot, at least we can make direct comparisons between different manufacturers' models. Well no. It’s not quite that simple either. You see, there are different ways of measuring the same space, which is why you might see some manufacturers using the terminology ‘Litres VDA’.

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Space war: Hatch v Sedan v SUV 

The VDA standard was originally published by the German Association of the Automotive Industry (Verband der Automobilindustrie, VDA). It was later incorporated into the international ISO standards and is part of the German standard DIN (Deutsche Institut für Normung). Not only a favourite for German brands, the VDA method also tends to be the approach taken by many other European, Japanese and Korean manufacturers too.

Calculating the volume of the boot space is done by literally filling it with one-litre blocks measuring 200mm x 50mm x 100mm. The amount of those blocks that can fit inside the boot at one time is the VDA number. As you might imagine it’s like an oversized puzzle with different stacking configurations likely to affect the outcome, so perfecting the loading technique is vital.

For hatchback cars or SUVs which have a more open luggage area, compared to the fully enclosed boot of a sedan, there are sometimes a few different luggage capacity numbers quoted in a single brochure. Typically they would be the volume of the luggage area up to the top of the rear seat, the volume up to this height with the rear seats folded down and the “maximum cargo volume” which is with seats folded down and loaded to the roof.

But, beware when doing your car comparisons because there’s another volume measuring method in use called the SAE standard.

For closed luggage areas like a sedan boot the SAE method also simulates packing with boxes. However, the boxes used represent differently sized luggage pieces from a 67 litre suit case to a 5.6 litre shoebox. There’s even a solid equivalent of a golf bag.

For open luggage areas SAE volumes move from the proven loaded volumes to an estimation of volume called a Cargo Volume Index. The luggage space is calculated by multiplying the height, width and length dimensions between specific points in the load space which are dependent on the vehicle body style (hatch, wagon, SUV etc).

These two recognised standards will rarely (if ever) give the same result. So how do we know that we’re comparing apples with apples when choosing a new car?

In some cases the luggage volume will be clearly described as “L (VDA)”, sometimes scouring through the specification fine print will clarify the measurement technique as either SAE or VDA.

Some manufacturers don’t offer the answer at all and leave us guessing, while some helpfully quote both figures. The main thing is that if luggage space is the deciding factor in your next car purchase, remember that when it comes to boot volume, things aren’t always as they first seem.