# Power tool vibration figures and HAVS explained

Source: https://drillandbit.co.uk/blog/power-tool-vibration-explained
Published: 2026-10-12
Publisher: Drill and Bit

**In short:** The vibration figure on a tool listing is the declared vibration emission in m/s², measured to a standard test, with an uncertainty K. It lets you compare tools, but real use can be higher. HSE sets a daily exposure action value of 2.5 m/s² A(8) and a limit of 5 m/s² A(8). Lower vibration tools, shorter use and breaks all reduce the risk of hand arm vibration syndrome.

Most power tool listings show a line such as vibration emission value 7.5 m/s², uncertainty K 1.5 m/s². It is easy to skip, but it matters if you use drills, SDS drills, multi-tools or saws for long periods. This guide explains what the numbers mean, how daily exposure adds up and what the HSE says about hand arm vibration for workers and keen DIYers.

## What the figures mean

The **vibration emission value**, written ah in m/s², is the average acceleration at the handle measured under a standard test for that kind of tool. Tools are tested in each mode, so an SDS drill may list separate figures for hammer drilling and chiselling, and a combi drill for drilling and hammer drilling. The **uncertainty K**, often 1.5 m/s², reflects variation in the test.

Declared values are useful for comparing similar tools. HSE notes that vibration in real use can be higher than declared, depending on the material, the accessory and how the tool is held, so treat the figure as a guide, not a guarantee.

| Field | Meaning |
| --- | --- |
| ah or vibration emission | Measured vibration in m/s² for a given mode |
| K | Measurement uncertainty in m/s² |
| Mode | The function tested, for example hammer drilling into concrete |
| Sound pressure and power | Noise in dB(A), with its own uncertainty |

Typical label fields

## How daily exposure adds up

Exposure depends on both the vibration level and how long your hands are actually on the working tool. HSE expresses daily exposure as A(8), an average over an eight hour day. Under the Control of Vibration at Work Regulations 2005, the **exposure action value** is 2.5 m/s² A(8) and the **exposure limit value** is 5 m/s² A(8).

HSE also uses an exposure points system to make this easier. Points per hour are roughly two times the vibration value squared, so a tool at 5 m/s² gives about 50 points an hour. 100 points a day reaches the action value and 400 points the limit. HSE publishes a calculator and ready reckoner for this.

## Why it matters

Long term exposure can cause hand arm vibration syndrome, which affects blood vessels, nerves and joints in the hands and arms, and carpal tunnel syndrome. Early signs include tingling, numbness and fingers going white in the cold. The damage can be permanent, so prevention is key for anyone who uses tools for hours each week.

Occasional DIY use rarely reaches the action value, but long sessions of chiselling, grinding or sanding can. Employers have legal duties to assess and control exposure; self employed trades should follow the same guidance.

Note: If you notice tingling, numbness or white fingers after using tools, stop and speak to your GP or occupational health adviser.

## Choosing lower vibration tools

Compare declared values for the same mode across similar tools. Many SDS drills and multi-tools have anti vibration handles or systems that reduce the figure. Brushless tools are not automatically lower in vibration, so check the listing.

Accessories matter too. Sharp bits and blades cut faster with less vibration. Balanced blades and the right blade for the material help. See [SDS drill settings](https://drillandbit.co.uk/blog/sds-drill-settings-explained) and [corded vs cordless SDS drill](https://drillandbit.co.uk/blog/corded-vs-cordless-sds-drill).

[Compare SDS drills](https://drillandbit.co.uk/best/best-cordless-sds-drills)

## Practical ways to reduce exposure

Small changes to how and how long you use a tool cut exposure a lot, at no cost.

- Use the right tool: an SDS drill for concrete rather than a combi drill working hard.
- Keep bits, chisels and blades sharp.
- Let the tool do the work and avoid gripping harder than needed.
- Take regular breaks and spread heavy jobs over several days.
- Keep hands warm and dry, which helps circulation.
- Consider hiring a bigger tool for big jobs, which finishes faster.

## Where to find more

HSE publishes guidance, the exposure calculator and advice for employers and workers on its vibration pages. Tool makers list vibration figures in manuals and on their UK websites, usually in the technical data.

For drilling technique that reduces strain, read [how to use an SDS drill](https://drillandbit.co.uk/blog/how-to-use-an-sds-drill), and for chiselling, [how to break up concrete with an SDS drill](https://drillandbit.co.uk/blog/how-to-break-up-concrete-with-an-sds-drill).

## Frequently asked questions

**What is a good vibration figure for a combi drill?** Lower is better, but compare the same mode. Drilling figures are usually much lower than hammer drilling figures.

**What does K mean on a vibration rating?** It is the measurement uncertainty, often 1.5 m/s².

**Does HAVS affect DIY users?** It is mainly a risk for regular long use, but long chiselling or grinding sessions can add up. Take breaks.

**Are anti vibration handles worth it?** Yes for regular SDS and chiselling work. They reduce the vibration reaching your hands.

## Buying guides on this topic

- https://drillandbit.co.uk/best/best-cordless-sds-drills
- https://drillandbit.co.uk/best/best-oscillating-multi-tools
- https://drillandbit.co.uk/best/best-combi-drill-kits

## Sources

- [HSE: vibration at work](https://www.hse.gov.uk/vibration/)