Calculator based on the regulations
Weighted medical disability calculator
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How does National Insurance combine several disability percentages?
National Insurance does not add percentages together. The highest impairment counts in full and each further one applies only to the capacity that remains. Impairments of 40%, 30% and 10% give 40% + 18% + 4.2% = 62.2%, rounded up to 63% when the degree confers a pension. The method is set by regs. 11(b) and 19A of the 1956 regulations.
The method in the regulations
| Step | Rule | Source |
|---|---|---|
| Order | Sort the impairments from highest to lowest | reg. 11(b) |
| Combine | The first in full; each next one times the remaining capacity: W + d × (100 − W) | reg. 11(b) |
| Limb ceiling | Several impairments of one joint, limb or eye cannot exceed the rate for its ankylosis, amputation or blindness | reg. 11(c) |
| Rounding | Where the degree confers a pension (20% or more for work injury), a fraction is rounded up; below that it stays | reg. 19A |
| Increase | The committee may increase by up to half; below 20% the result cannot exceed 19% | reg. 15 |
| 65% and above | Where the person cannot work, the committee may set 100% | reg. 16 |
Worked examples
- 40%, 30% and 10%: 40 + 18 + 4.2 = 62.2%, rounded up to 63%.
- 20% and 10%: 20 + 8 = 28%.
- 25%, 15% and 10%: 25 + 11.25 + 6.375 = 42.6%, rounded up to 43%. This meets the medical threshold for general disability.
What the calculator does not include
- It does not apply reg. 15 (increase), reg. 16 or reg. 11(c); those are decisions for the medical committee.
- For general disability the medical threshold is 60%, or 40% where one impairment is at least 25% (s. 208 of the National Insurance Law). Meeting it is not by itself entitlement to a pension.
- The percentage for each impairment is set under the impairment items in the schedule to the regulations, in the committee's minutes.
- For general disability, percentages are set under the 1984 regulations, with a different list of impairments. The threshold check here is only an indication.
Sources
This is general information and a calculation under the law and regulations. It is not an assessment of a particular case and not personal legal advice.
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