The payment is the full premium plus 2%
While you worked, the employer usually covered part of the premium. On COBRA that subsidy disappears: you pay what you paid as an employee plus what the employer used to contribute, and the plan may add a 2% administrative charge on top, which puts the payment at 102% of the plan cost.
The arithmetic is short. The administrative charge is 2% of the full monthly premium, rounded to the cent; the monthly payment is the premium plus that charge, rounded again; the total for the period is the monthly payment times the number of months. At the default $620 premium the charge is $12.40, the payment $632.40, and eighteen months come to $11,383.20.
The 102% figure is what this page prices at for every period it offers. During a disability extension a plan may charge the disabled beneficiary up to 150%, but the 29-month row here is computed from the same 102% payment as the other two rows, so treat it as the standard charge rather than the ceiling the law allows in that one case.
The periods the law allows
A job loss or a reduction in hours buys 18 months of continuation. If you qualify for Social Security disability within those 18 months, the coverage extends another 11 months, to 29 in total, and during that extension a plan may charge the disabled beneficiary up to 150% of the plan cost rather than 102%. Death, divorce or legal separation, Medicare entitlement, or a dependent losing status each buy 36 months.
The period table runs all three published lengths with the same monthly payment and changes only the number of months, so it answers a narrow question honestly: what the same plan costs if continuation lasts 18, 29 or 36 months. It does not pretend that different qualifying events carry different monthly rates; your notice sets the rate, and the event decides only how long the coverage can run.
The select offers exactly those three periods, and a value outside the set is snapped back to 18 months, so a stray link cannot make the page print a made-up month count. The months are the only figure that changes between the rows; the premium, the 2% charge and the monthly payment stay fixed.
When the clock starts
The employer must tell the plan within 14 days of the qualifying event, the plan usually has another 14 to send the election paperwork, and you then have 60 days - counted from the later of the notice or the loss of coverage - to elect. Coverage is retroactive to the day it would otherwise have been lost, so a serious illness inside that window is still covered once you elect and pay.
Premiums are due within 45 days of the election. None of this enters the multiplication on this page: the timeline changes whether the coverage is actually in force when you need it, while the multiplication only says what the coverage costs once it is.
That distinction is why the timeline sits in the table footer instead of being folded into the total. A household that misses the election window does not save the premiums; it loses the coverage and keeps the medical bills, which is a very different number from the one in the headline.
What this page does not guess
The page does not know your plan rate - only the plan administrator notice prints that figure - so the premium is an input, and the output is only as good as the notice you read it from. A premium of zero returns a single warning instead of a table, because there is no continuation payment to price.
It does not model a severance package that subsidizes COBRA, a marketplace plan that may be cheaper, or the premium tax credit that could change that comparison. Network, deductible, whether your doctors stay in network and how the premiums are taxed all sit outside this arithmetic, and they are often what decides the choice.
What it does give you is the number the decision starts from: the monthly payment and the total for the legal maximum period that applies to your event. Put those beside the same two figures for the alternatives you are actually considering, and the comparison stops being a guess about which option sounds cheaper.
Danfio