Blade life
Blade life
A handful of listings on this site put a period on the cutting part they sell, and the rest say nothing at all. Where a figure exists it is the seller’s expectation rather than a measurement of your beard, and the useful thing to do with it is turn it into a date you can remember rather than a claim you can argue with.
Three listings quoted on this site state how long a cutting part is expected to last: Philips Norelco 2400 Rotary Shaver X3001/90, Philips OneBlade 360 Face QP2724/90 and Philips OneBlade 360 Face and Body QP2834/70.
What a figure covers
A stated blade life is a period in months, and the period runs from the day the blade goes into service rather than from the day the box arrives. A spare blade sitting in a drawer is not aging in the way the number describes.
It assumes ordinary use, which the listing does not define. A blade taken through dense hair every day is doing more work than one used twice a week, and the same figure is printed on both.
Where a listing states two years for a set of cutters, that is a statement about the whole cutting assembly rather than about a single replaceable edge, and the two are not the same kind of replacement at all.
When nothing is stated
Most appliances here print no blade life at all. That is not a hidden claim of permanence; it is silence, and the figure to use instead comes from the documentation that arrived in the box.
The tool below is for appliances that state a period. Where none is stated, there is nothing honest to put into it, and inventing a number to fill the field would be exactly the habit this site exists to avoid.
A dulled blade
A cutting part reaching the end of its life pulls rather than cuts. The appliance sounds the same and feels different, and the change is gradual enough that most people adjust their technique instead of noticing it.
The practical test is time rather than sensation: a blade replaced on schedule never has to be judged. That is the whole argument for putting the interval somewhere you will see it.
Replacement as ownership
A four-month blade comes round again three times in a year, which is the stated figure divided into twelve and nothing more, and it does so every year for as long as the appliance stays in service. That is not a decision taken later and separately; it is part of what owning this kind of appliance involves, and the figure is printed on the listing before anything is bought.
It runs the other way too. Where a listing puts two years on a whole cutting assembly, the interval is long enough that most people forget it exists, and what eventually gets replaced is the assembly rather than one edge.
Replacement interval
Months the listing states
4 stated
Only for an appliance whose listing prints a blade life. Where none is printed, there is no figure to put here, and the one to use comes from the maker’s own documentation.
Shaves in a week
- Changes in a year
- 3
- Shaves per blade
- 87
- Next change
- 4 months after it goes into service
Counted in months from the day the blade starts being used, not from a date on a calendar.
The arithmetic
- replacements per year = 12 ÷ stated months
- shaves per blade = stated months × 52 ÷ 12 × shaves per week
- next change = stated months after the day the blade went into service
What it does not account for
- How coarse the hair is, which changes how hard a blade works per minute.
- How the appliance is cleaned, since hair left packed against an edge is not a neutral condition.
- Time the appliance sits unused, which the stated period counts and your beard does not.
- Whether the blade was stored dry, which decides what corrodes before anything dulls.
Where this goes wrong
Counting from the purchase
A spare bought at the same time as the appliance is treated as though it aged on the shelf, and gets thrown away with life left in it.
Start counting on the day a blade first goes onto the appliance and write that date down.
Waiting for it to feel blunt
The change is gradual, technique adapts around it, and the blade is judged only after it has been pulling for weeks.
Replace on the interval rather than on the sensation, which is the only reliable signal available.
Inventing a figure
An appliance that states nothing gets assigned a period borrowed from a different appliance, and the interval means nothing at all.
Use the documentation that came with the appliance, or accept that there is no figure to work from.
Cautions
- NoteReplacement foils, cutters and heads come from the list printed in the appliance’s own documentation. A part that seats is not the same as a part the maker names.
- StopTwo things mean stopping rather than taking one more pass. Skin that is broken, raised, sore or already inflamed, which is a doctor’s call and not something to draw a blade across. And a line so far out of true that a shorter setting only chases it, which is a barber’s. Neither of them improves by carrying on.
- StopA shaver or a trimmer belongs to one person. Shaving injures skin at a scale too small to notice, and whatever sits on the blade goes into that injury.
Where to look next
- Single-Blade Hybrids
The group where a replacement interval is part of the purchase rather than an afterthought.
- Single-blade hybrids
Why a single edge that has dulled pulls instead of cutting, and where that matters most.
- Power and Refills
Where the consumables live, including a cartridge made by a company other than the appliance maker.