1:43 scale is a popular size for diecast vehicles. It matches the size of O scale trains in the UK. It doesn’t match the size of US O scale trains. But how big is 1:43 scale? And should you care about the difference?

A 1:43 vehicle is about 4.5 inches long, which is about 10% oversize compared to 1:48. You’ll notice the difference if the two are side by side, but there are ways to compensate for the difference too.

## How 1:43 scale is calculated

I scaled two copies of the same image to show the relative difference between 1:43 and 1:48 scale. A 1:43 scale Honda Accord is about 4.5 inches long while a 1:48 is about 4 inches. Holding them both in your hand, you’ll notice the difference.

1:43 is just a ratio. It may seem like an odd ratio to use, but the British decided to use it because there’s a convenient shortcut to calculating it. Simply measure the item you’re modeling in feet, then convert it to metric, using a measurement of 7 millimeters to represent feet.

An adult male is approximately six feet tall. So a 1:43 model of an adult male would be 6×7 millimeters (42 mm) tall. Converting it back to imperial units, that’s 1.65 inches tall. Jada Metalfigs toys are about 1:43.

Or, if you have the dimensions in millimeters, you can simply divide the measurement in millimeters by 43. Do whichever is easiest. You’ll get more precision working in millimeters though.

Applying it to vehicles, a Honda Accord is 16 feet long, 6 feet wide, and 4.8 feet tall. So a 1:43 Honda Accord would be 112mm long, 42mm wide, and 33.6mm tall. That’s 4.4 inches long, 1.65 inches wide, and 1.3 inches tall.

## How big is 1:43 scale compared to 1:48?

1:43 vehicles are popular worldwide, and their popularity dwarfs that of 1:48 trains. That’s why you have much better luck finding 1:43 vehicles in discount stores than O scale trains. But there’s cross-pollination between the two markets. Train fans use 1:43 vehicles on their layouts because it’s close, and true 1:48 vehicles are scarce. Diecast fans who want to make dioramas for their cars may want to use O scale buildings and figures and trees, because 1:43 figures and buildings are somewhat scarce.

For the majority of hobbyists, the two scales are close enough.

Take an adult male figure, for example. A 1:43 adult male is 42mm or 1.65 inches tall. A 1:48 adult male is 1.5 inches, or 38mm tall. So the difference between the two is about 10 percent. If we go the other direction, a proper 1:43 figure intended to represent a 6-foot human would represent a 6.6-foot human in 1:48. 6.6 feet is 6 feet, 7 inches, or 2 meters tall. That’s much taller than average, but not outside the realm of expectation. Many professional athletes are that tall.

Going the other way, a 1:48 figure represents a 5.36 foot male in 1:43. That’s 1.6 meters tall, or 5 foot, 4 inches. That’s short, but again, not outside the realm of expectations. Davy Jones of the Monkees was 5 foot, 3 inches.

A proper 1:43 Honda Accord should be 115 mm long by all rights (if you work entirely from metric units to reduce rounding errors). That’s 4.5 inches long. A proper 1:48 Honda Accord would be 102.77mm long. That’s 4 inches long.

If you’re holding the model in your hand, you’ll notice the difference. But from a distance of a couple of feet you won’t. Especially once you reach your 40s.

## The effect of rounding errors

There’s one other problem with asking how big 1:43 scale is. Rounding errors. If you’re reading carefully, I contradicted myself on the size of that Honda Accord. In one section I said it should be 112mm long, and in the other I said 115mm.

If I measure in Imperial units and round off to the nearest quarter or 1/8 inch, I introduce a rounding error. If I use someone else’s Imperial measurement, they may have rounded it differently than I would have. Or they may have converted a metric measurement and rounded it differently than I had. Then, when I scale it, I introduce another rounding error.

The result is some 1:43 models are a bit oversize or a bit undersize. The same is true of 1:48s.

## Will you notice the difference?

With two models side by side you’ll definitely notice the difference. If you see Honda Accords next to EMD SD70 locomotives every day, then a 1:43 Accord next to a 1:48 SD70 on your layout might look wrong to you.

Chances are you don’t see the two side by side all the time. If there’s some distance between the two and the SD70 is moving, you’re even less likely to notice. And if you’re some distance away and all the other factors are in play, the difference diminishes even more.

But if you’re a 1:48 modeler and a stickler, old 1:48 Dinky vehicles are an option for you.