Correction Note: HAVS Calculator and Trigger Time Values Updated to HSE Canonical Formula
What Was Corrected
On 18 May 2026 we updated the points-per-hour formula used across the site so its output matches the points-per-hour values HSE tabulates on the assess-the-risks guidance page (Table 2). HSE publishes that table and an Excel calculator rather than the formula itself, and labels its table values "approximate" (rounded — e.g. it shows 20 points/hour at 3 m/s² where the exact figure is 18). The expression below is the standard derivation that gives the exact points-per-hour value HSE's table rounds.
The corrected formula:
Points per hour = 2 × magnitude²
The previous formula on the site treated the daily-total-at-8-hours expression (magnitude ÷ 2.5)² × 100 as if it were points-per-hour for any duration. That overstated points by a factor of eight. The EAV/ELV threshold checks themselves still flagged correctly (a worker over the limit was still shown as over), but the displayed point totals, time-to-EAV values, and time-to-ELV values were all eight times higher than HSE's published numbers.
Why It Matters
Verify any of these against HSE's Table 2 and the corrected values now line up (HSE's table is rounded to "approximate" values; the formula column below is the exact figure, with HSE's rounding shown for comparison):
| Vibration (m/s²) | Points/hour (exact, 2 × m²) | Points/hour (HSE Table 2, rounded) | Time to EAV (100 pts) | Time to ELV (400 pts) |
|---|---|---|---|---|
| 3 | 18 | 20 | 5h 33m | 22h+ |
| 5 | 50 | 50 | 2h | 8h |
| 7 | 98 | 100 | 1h 1m | 4h 5m |
| 10 | 200 | 200 | 30m | 2h |
| 12 | 288 | 300 | 21m | 1h 23m |
| 15 | 450 | 450 | 13m | 53m |
If you have a saved exposure calculation, risk assessment, or log sheet generated by the site before 18 May 2026, the point totals on it are eight times the canonical HSE values. The threshold decision (EAV reached? ELV exceeded?) will usually still be correct in direction, but the numbers and the trigger-time estimates will not match what HSE publishes.
Components Updated
The following components and posts had their formula corrected:
- The HAVS Exposure Calculator
- The HAVS Trigger Time Chart
- The HAVS Log Sheet Template (both the on-screen preview and the exported PDF)
- The pillar guide How to Calculate Hand Arm Vibration Exposure
- The reference HAVS Time Limits: Trigger Times for Common Construction Tools
- The quick-reference HAVS Exposure Limits: EAV and ELV
- The HAVS Risk Assessment Guide
- The methodology reference in Hand Arm Vibration Testing
The HAVS Points System Explained guide already used the HSE-canonical formula throughout.
How the Error Crept In
The expression (A(8) ÷ 2.5)² × 100 is correct as a points-equivalent for a worker's daily A(8) at an eight-hour reference period. Applied per-hour with the tool's raw magnitude in place of A(8), it overstates by a factor of eight. The initial seed cycle of the site used this expression as the per-hour formula. Subsequent content reviews verified the methodology against the regulations without re-deriving the per-hour values against HSE's published Table 2 — so the error propagated until a fresh-eyes fact-check pass on 18 May 2026 compared every tool component output against the HSE table line by line.
If you spot any value on the site that still doesn't match HSE Table 2, please flag it via the contact link in the footer.
Sources
This guide is for general information only. It is not a substitute for professional health and safety advice.