Disability income estimator

Published 2026-10-01 · Last updated 2026-10-01.

What you enter

The working HTML tool (disability-estimator.html, in this same folder) uses only figures you enter. No insurer rate is stored in it.

• Monthly income: your usual monthly income before tax, as you understand it. Use a figure you can check against a payslip or accounts, not a round guess.
• Replacement share you want to test: the percentage of that income you want the estimator to aim for, entered by you. Policies commonly replace only part of income, not all of it — the tool does not assume a share for you; you choose the share to test and can try several.
• Existing monthly disability benefit: any monthly benefit you already hold, from an employer plan or a policy you own. Enter zero if you hold none. Do not count sick pay you are unsure about, and do not count Social Security Disability Insurance as a certain benefit here — SSDI eligibility and timing are separate questions, and this estimator is not a benefits determination.
• Monthly essential expenses: the spending you could not stop if income stopped — housing, food, utilities, transport and debt payments, as you define them.
• Waiting period in months: the elimination period you want to test — the months before a long-term benefit would start. The tool multiplies your monthly gap or expenses, as shown, to size the savings bridge for that period.

All inputs must be numeric and non-negative, and the replacement share must sit between 0 and 100. The tool rejects anything else and says so, rather than silently computing from a bad input.

Your income gap — how the tool calculates it

Target, gap, annual gap, savings bridge

The tool calculates: target monthly income = monthly income × replacement share; monthly gap = target monthly income − existing monthly benefit. If the existing benefit already covers the target, the gap is zero or negative, and the tool says so plainly — a negative gap is a surplus on the assumptions entered, not a reason to buy more cover.

It also shows the annual gap (monthly gap × 12) and, separately, the savings bridge for the waiting period you entered: the amount of savings you would need to cover the gap, or your essential expenses, across those waiting months. Read those two numbers differently. The annual gap describes an ongoing shortfall if the disability lasts. The savings bridge describes a one-off reserve for the wait before a benefit starts. A plan that covers one but not the other still leaves a hole.

Short vs long term (general)

Short-term and long-term disability cover are two halves of one plan, not rivals. Short-term cover typically starts within days or a couple of weeks and pays for months, usually within the first year. Long-term cover waits out an elimination period measured in weeks or months — commonly around 90 days, though periods vary — and then pays for years, sometimes to retirement age. The two are designed to stack: short-term bridges the wait, long-term carries the longer absence.

The most common planning mistake is a mismatch at the handover. If short-term cover ends before the long-term elimination period ends, the gap between them is unprotected income. Size the long-term waiting period against the short-term benefit's actual duration, and size your savings bridge against the same wait. This page's estimator lets you test that wait directly by changing the months you enter.

ILLUSTRATIVE EXAMPLE — not a policy fact

A worker enters, purely to show the arithmetic: monthly income $5,000; replacement share to test 60% (target $3,000 a month); existing monthly benefit $0; essential expenses $2,800 a month; waiting period to test 3 months. The monthly gap is $3,000 − $0 = $3,000, the annual gap is $36,000, and a savings bridge for the 3-month wait at the gap level is $9,000 (at the expenses level, $8,400). If the same worker entered an existing benefit of $1,500, the gap would fall to $1,500 a month. These figures are ILLUSTRATIVE ONLY, chosen to demonstrate the tool; they describe no real worker, no real policy and no insurer's benefit.

What to check — before you treat the gap as a shopping list

• Your employer's plan, if any. What does it actually pay, for how long, and after what wait? An employer short-term plan and an employer long-term plan are different benefits with different terms.
• The definition of disability in any policy you hold. Some policies pay when you cannot do your own occupation; others pay only when you cannot do any occupation. That definition changes the value of the cover more than the headline percentage does.
• Benefit duration and caps. A monthly benefit that stops after two years is a different product from one that runs to retirement age, even at the same monthly amount.
• Offsets. Some policies reduce their benefit by other income you receive. Ask whether an existing benefit would be reduced, not just whether it exists.
• SSDI, separately. Social Security Disability Insurance is a government benefit with its own eligibility rules and timing. It is context for this page, not an input you should treat as guaranteed income in the estimator.