In our first guide, Car Sound Deadening: The Complete Guide, we covered why road noise enters your vehicle, how sound deadening helps reduce it, and which areas of your vehicle are worth treating.

This follow-up answers one of the most common questions we receive:

How much sound deadening do I actually need?

By the end of this guide, you'll know how to measure the areas you want to treat, calculate the approximate square metres required and convert that into the number of linear metres to order.

The aim is simple: order enough material to complete the job without unnecessarily over-ordering or running short halfway through the installation.

First, a Myth Worth Clearing Up

You don't necessarily need to cover every square centimetre of metal with every type of sound-deadening material.

Different sound-control materials work in different ways.

Dense constrained-layer damping materials are primarily designed to reduce panel vibration and resonance and can often be effective without completely covering a panel.

Foam sound deadening works differently.

Swift Deals foam sound deadening acts primarily as an absorption and decoupling layer. It helps reduce airborne road noise, softens higher-frequency noise and provides useful thermal insulation.

Because foam works by covering and decoupling surfaces, more complete coverage of the areas being treated generally provides better results.

So rather than asking:

"How much material do I need for my whole car?"

A better question is:

"Which areas am I treating, and how much material do I need to cover those areas?"

Once you know that, the calculation is easy.

Which Areas Should You Measure?

Not every part of a vehicle contributes equally to cabin noise.

Here are some common areas to consider:

Area	Why Treat It?	Typical Area
Doors	Helps reduce panel resonance and external road noise and can improve the acoustic environment around speakers.	Approx. 0.5–0.8 m² per door
Floor	A major path for tyre, road and drivetrain noise.	Approx. 2.5–4 m²
Boot / cargo area	Helps reduce road, suspension and rear tyre noise.	Approx. 1–2 m²
Roof	Helps reduce rain noise and provides additional thermal insulation.	Approx. 1.5–2.5 m²
Firewall	Helps reduce engine and drivetrain noise entering the cabin.	Approx. 0.5–1 m²
Wheel arches	Important areas for tyre, road and stone noise where accessible.	Approx. 0.5–1 m²

These figures are only a guide.

Vehicle dimensions vary considerably, particularly between small cars, SUVs, 4WDs, utes and vans.

For the most accurate result, measure your own vehicle.

The Basic Calculation

You don't need complicated measurements.

For most areas, use:

Length × Width = Area

For example, if part of your vehicle floor measures:

2.0 m long × 1.4 m wide

then:

2.0 × 1.4 = 2.8 m²

Do the same for each area you're treating and then add the results together.

Example

Floor: 2.8 m²

Doors: 2.2 m²

Boot: 1.8 m²

Total:

2.8 + 2.2 + 1.8 = 6.8 m²

How to Measure Irregular Areas

Vehicle interiors obviously aren't perfect rectangles.

You'll encounter:

• transmission tunnels
• wheel arches
• curved floor sections
• seat mounts
• speakers
• wiring
• brackets
• trim mounting points

You don't need to measure every curve precisely.

Instead, divide complicated areas into several simple shapes and calculate them separately.

For example, divide the floor into:

Front floor + rear floor + transmission tunnel

If you're measuring a transmission tunnel, use a flexible tape measure to measure up one side, across the top and down the other side, rather than measuring only its visible width from above.

For wheel arches and other curved areas, estimate the approximate rectangular area surrounding the section you intend to cover.

The objective is a practical ordering estimate, not a millimetre-perfect engineering measurement.

From Measurements to Metres

This is where ordering Swift Deals sound deadening becomes particularly simple.

Our automotive sound deadening is supplied:

1 metre wide

That means:

1 linear metre × 1 metre wide ≈ 1 m²

So if your project requires approximately:

6 m²

you'll need approximately:

6 linear metres

before adding your cutting allowance.

Quick Reference

Coverage Required	Approximate Roll Length
3 m²	3 linear metres
5 m²	5 linear metres
8 m²	8 linear metres
10 m²	10 linear metres
12 m²	12 linear metres
15 m²	15 linear metres
20 m²	20 linear metres

Typical Project Estimates

If you don't want to measure every area before getting started, these figures can provide a rough starting point.

Project	Typical Area
Doors only	Approx. 2.5–3 m²
Doors + floor	Approx. 5–7 m²
Major areas of a small car	Approx. 8–12 m²
Major areas of a medium SUV / 4WD	Approx. 12–18 m²
Large 4WD / van	Approx. 18–25+ m²

These are estimates only.

Vehicle sizes and the amount of coverage chosen vary considerably, so we recommend measuring your vehicle before ordering larger quantities.

A Worked Example

Let's say you're treating a typical sedan:

Four doors:

2.4 m²

Floor:

3.5 m²

Boot:

1.5 m²

Total:

7.4 m²

Now add approximately 10% for cutting, curves and offcuts:

7.4 × 1.10 = 8.14 m²

Because it's better to have a little material left over than run short:

Round up to approximately 9 linear metres.

That's it.

Always Allow a Little Extra

Whatever your measurement comes to, we recommend adding approximately 10–15%.

Why?

Because you'll inevitably have some material left over when cutting around:

• door mechanisms
• speakers
• wheel arches
• curves
• seat mounts
• wiring
• brackets
• irregular floor sections

If your calculation comes to:

8.4 m²

don't round down to 8 metres.

Allow for cutting and fitting and round your final requirement up.

Running short halfway through an installation can mean having to stop the project while the vehicle is already partially disassembled.

A small allowance makes the installation much easier.

Choosing the Right Swift Deals Sound Deadening

Once you know how much material you need, you can decide which thickness is appropriate for each part of your vehicle.

Swift Deals offers automotive foil backed sound-deadening options including:

6 mm sound deadening

10 mm sound deadening

15 mm sound deadening

You don't necessarily need to use the same product everywhere.

For example, space behind door trims may be different from the available space underneath carpet or within a cargo area.

If you're using different products in different parts of the vehicle, calculate the square metres required for each product separately.

For more information about choosing the appropriate material for different areas of your vehicle, see our Car Sound Deadening: The Complete Guide.