HAVS Points System Explained: How to Convert m/s² to Exposure Points
Why HSE Uses Points Instead of A(8)
The A(8) value — daily vibration exposure normalised to 8 hours, measured in m/s² — is the official unit in the Control of Vibration at Work Regulations 2005. But A(8) requires a square root in every calculation and turns "I used the breaker for 15 minutes and the grinder for 45" into algebra most supervisors don't want to do at the end of a shift.
The HSE exposure points system gives you the same answer in arithmetic. Points add linearly across tools and across hours; there are no square roots. You compare the daily total against two fixed numbers — 100 (EAV) and 400 (ELV) — and you don't need to think about A(8) at all.
This guide explains the points system, the conversion formula between m/s² and points, and shows how to use it on site without spreadsheets.
The Conversion: m/s² to Points per Hour
The relationship between A(8) and exposure points is fixed:
- EAV: 2.5 m/s² A(8) = 100 exposure points
- ELV: 5 m/s² A(8) = 400 exposure points
Both thresholds correspond to the same exposure expressed in different units. Points scale with the square of vibration magnitude. The formula for converting a tool's vibration magnitude into points per hour of use is:
Points per hour = 2 × (magnitude in m/s²)²
(This is the HSE-canonical formula. If you used our calculator before 18 May 2026, see the correction note explaining the points-per-hour fix — earlier values were overstated by a factor of eight.)
Worked through:
- Tool at 2.5 m/s² → 2 × 2.5² = 2 × 6.25 = 12.5 points per hour. 8 hours of use = 100 points (exactly the EAV).
- Tool at 5 m/s² → 2 × 5² = 2 × 25 = 50 points per hour. 8 hours = 400 points (exactly the ELV).
The factor 2 normalises to an 8-hour reference. The squaring is what makes a small jump in m/s² produce a large jump in points — a tool at 10 m/s² is not "twice as bad" as one at 5 m/s², it's four times as bad in damage terms.
Why the square law matters
The square law is the single most counterintuitive part of HAVS exposure. Workers and supervisors often reason linearly: "double the vibration, double the risk." It's not. Double the vibration is four times the points per hour. The implications:
- A worker using a 12 m/s² heavy breaker for 15 minutes accumulates 72 points — almost three-quarters of the EAV in a quarter of an hour.
- The same worker using a 3 m/s² SDS rotary for the rest of the 8-hour shift accumulates 138 points — total 210 points, well past the EAV and over half-way to the ELV.
Without the square law you'd dismiss the 15-minute breaker burst as trivial. The points system makes it visible.
Points-per-Hour Table for Common Construction Tools
These are typical manufacturer-declared values from HSE's published guidance and common manufacturer data sheets. Your actual tools may differ — always verify against the manufacturer's data sheet first.
| Tool type | Typical magnitude (m/s²) | Points per hour | Hours to EAV | Hours to ELV |
|---|---|---|---|---|
| SDS rotary hammer drill (small) | 3 | 18 | 5h 33m | 22h+ |
| Angle grinder (small, 4½") | 4 | 32 | 3h 8m | 12h 30m |
| Angle grinder (large, 9") | 6 | 72 | 1h 23m | 5h 33m |
| Hammer drill (corded) | 9 | 162 | 37m | 2h 28m |
| Concrete breaker (medium) | 12 | 288 | 21m | 1h 23m |
| Concrete breaker (heavy) | 14 | 392 | 15m | 1h 1m |
| Demolition pick | 18 | 648 | 9m | 37m |
| Petrol disc cutter | 6 | 72 | 1h 23m | 5h 33m |
| Plate compactor | 8 | 128 | 47m | 3h 8m |
For an interactive lookup of vibration magnitudes by tool model, see the HAVS Trigger Time Chart. For multi-tool calculation in one step, the HAVS Exposure Calculator handles the points maths automatically.
Worked Example: Three-Tool Shift
A site supervisor needs to check whether a worker's planned shift will exceed the EAV.
Plan:
- 30 minutes on a heavy breaker (12 m/s²)
- 90 minutes on a 9" angle grinder (6 m/s²)
- 2 hours on a hammer drill (9 m/s²)
Step 1 — Points per hour for each tool:
| Tool | Magnitude | Points per hour |
|---|---|---|
| Heavy breaker | 12 m/s² | 2 × 12² = 288 |
| Large grinder | 6 m/s² | 2 × 6² = 72 |
| Hammer drill | 9 m/s² | 2 × 9² = 162 |
Step 2 — Points per actual use:
| Tool | Points per hour | Time | Points accrued |
|---|---|---|---|
| Heavy breaker | 288 | 0.5 h | 144 |
| Large grinder | 72 | 1.5 h | 108 |
| Hammer drill | 162 | 2.0 h | 324 |
| Total | 576 |
Step 3 — Compare to thresholds:
- 576 points > 400 ELV — the worker will exceed the legal maximum.
- Action: shorten the hammer drill time, rotate the worker out, or split the breaker work between two operatives.
The arithmetic is simple. The decision — what to actually do about it — is the supervisor's call, framed by the HAVS control measures menu.
The Reverse Calculation: Points Back to A(8)
If you only have a points total and need the A(8) value (e.g., for a regulator query or a health surveillance referral), the inverse formula is:
A(8) in m/s² = √(points ÷ 50) × 5
Or, simplified for the two key thresholds:
- 100 points = 2.5 m/s² A(8) (EAV)
- 400 points = 5 m/s² A(8) (ELV)
- 200 points ≈ 3.54 m/s² A(8)
- 50 points ≈ 1.77 m/s² A(8)
The square root in the reverse direction is why HSE keeps the forward arithmetic simple — supervisors do the points calc, and the A(8) value is computed only when needed for formal records or external reporting.
Common Mistakes in the Points System
Using the wrong magnitude. Always start with the tool's actual declared value, not an "around 8" estimate. A 1 m/s² error at the 6 m/s² level changes points-per-hour from 72 to 98 — a 36% swing. Errors compound quickly.
Forgetting tool wear. A 5-year-old grinder vibrates more than the manufacturer's test value. Where the declared value may underestimate real exposure, HSE publishes typical-in-use vibration values for common tool types — see the HSE assess-the-risks guidance for the tabulated values. Use these when the tool is worn, modified, or run differently from the manufacturer's test conditions.
Adding points instead of points-per-hour. A worker who uses a 12 m/s² breaker for 15 minutes and a 6 m/s² grinder for 45 minutes does NOT accumulate (288 + 72) = 360 points. They accumulate (288 × 0.25) + (72 × 0.75) = 72 + 54 = 126 points. Always multiply points-per-hour by actual hours-on-tool before adding.
Ignoring sub-2.5 m/s² tools. A tool at 2 m/s² produces 8 points per hour. Used for a full 8-hour shift, that's 64 points — alone it doesn't hit the EAV, but it's a meaningful contribution to a multi-tool day.
Where the Points System Comes From
The exposure points system is HSE guidance, not statutory text. The Control of Vibration at Work Regulations 2005 set thresholds in A(8) (m/s²), but HSE's published exposure calculator guide uses points throughout because it's the format supervisors and small employers find practical. Both A(8) and points refer to the same underlying calculation — the points system is just easier arithmetic.
The two systems are interchangeable: 100 points = 2.5 m/s² A(8) = EAV; 400 points = 5 m/s² A(8) = ELV. HSE inspectors accept either format in records as long as the calculation is sound.
When to Use Which System
Use points on site. Supervisors calculating daily exposure, log sheets, toolbox talks, on-site decisions about rotation — points are quicker, easier to add across tools, and require no calculator.
Use A(8) for formal records and referrals. Risk assessment documents, regulator correspondence, occupational health referrals — A(8) is the statutory unit and looks more rigorous. Convert points → A(8) at the end of the shift if needed.
Use both in training. New supervisors should understand both so they can talk to inspectors (A(8) speakers) and crews (points speakers) without translation friction.
Summary
The HAVS exposure points system converts vibration magnitude into simple-to-add daily exposure values:
- Points per hour = 2 × (magnitude in m/s²)²
- Multiply points-per-hour × actual hours on the tool for each tool
- Add across tools for daily total
- Compare to EAV (100) and ELV (400)
- Above 100 → action required; above 400 → stop, fix, record
The square law is what makes the system informative — short bursts on high-vibration tools matter more than the linear arithmetic suggests. Use the HAVS Exposure Calculator for multi-tool shifts, or print the points-per-hour table above for on-site reference.
For the legal framework these calculations support, see our guide to the Control of Vibration at Work Regulations 2005. For the underlying exposure limits in A(8) form, see the EAV and ELV quick reference.
Sources
This guide is for general information only. It is not a substitute for professional health and safety advice.