TL;DR
The fifty percent rule says replace anything whose repair quote exceeds half the cost of buying it new. Adjust it down to about one third once the item is past the midpoint of its expected lifespan, because a second failure is usually close behind the first. Those two steps settle most household repair decisions in under a minute.
What Is the Fifty Percent Rule?
The fifty percent rule is a decision shortcut: if a repair costs more than half of replacement, replace. It exists because people badly overweight what they already paid and badly underweight the failures still ahead. One ratio removes both biases and gives a defensible answer fast.
The rule is not a law of physics. It is a heuristic borrowed from fleet and facility management, where someone has to make hundreds of these calls a year and cannot deliberate over each one. Applied at home it is accurate enough to be useful and simple enough to actually get used.
The value is in the speed. Most people do not agonize over a decision because it is genuinely close -- they agonize because they have no rule. Having one turns a week of dithering into a two-minute comparison, which is the whole point of clean it or replace it thinking generally.
How to Apply It in Under a Minute
Get the total repair cost, not the part cost. Include the diagnostic or service call fee if it will not be credited toward the work, plus tax, plus any trip charge. That total is the honest number.
Get the true replacement cost, meaning what an equivalent item sells for now, not what you paid. Include delivery, installation, and haul-away where those apply, since they are real money.
Divide the first number by the second. Above 0.50, replace. Below 0.50, repair. That is the whole calculation.
Do not include the original purchase price anywhere in the math. What you paid three years ago is gone either way, and letting it into the equation is the single most common way people talk themselves into a bad repair.
The Age Adjustment That Makes the Rule Work
A flat fifty percent line ignores the most important variable, which is how much life is left. The fix is to move the line based on where the item sits in its expected lifespan.
If the item is in the first half of its expected life, fifty percent is right. If it is past the midpoint, use one third. If it is past roughly three quarters of its expected life, treat almost any significant repair as a replacement.
Expected lifespans are easy enough to estimate. Washing machines and dishwashers commonly run ten to thirteen years. Refrigerators run twelve to fifteen. Vacuums run five to ten. Small kitchen appliances run five to ten. Cordless tools last as long as their battery packs, which is usually three to five years.
The reason the adjustment matters is that failures cluster. Seals, bearings, pumps, and boards tend to reach the end of their service life around the same time, so a repair at year eleven often buys months rather than years.
Worked Example: A Ten-Year-Old Washer
Suppose a washing machine is ten years old, the drain pump has failed, and the quote is $250 to $300 including the service call. A comparable replacement is $600 to $700 delivered.
The raw ratio is roughly 0.40 to 0.50, which sits at or under fifty percent and looks like a repair. But the machine is at roughly the midpoint or past it, so the line moves to one third, or roughly $200 to $235. The quote lands over the adjusted line, which means replace.
If the same machine were four years old, the ratio would be well inside the fifty percent line and the repair would be an easy yes. Nothing about the part changed -- only the amount of remaining life. That is exactly the reasoning behind repair or replace a washing machine as a standalone decision.
Worked Example: A Blender and a Dishwasher
A blender in the $60 to $80 class with a dead motor gets a $100 to $120 quote. The ratio is well past 1.0, far beyond the line, so it is a replacement. In practice the diagnostic fee alone decided it, which is why when a small appliance repair is worth paying for is such a short list.
A six-year-old dishwasher with a failed door latch gets a $140 to $180 quote against $650 to $750 for a comparable replacement installed. The ratio is roughly 0.20 to 0.28, the machine is not yet past its midpoint, and the part is a discrete mechanical failure rather than a symptom of general wear. That is a clear repair, and it matches how repair or replace a dishwasher usually resolves at that age.
Notice that the same rule produced opposite answers without any hand-wringing. That is what a good heuristic does.
When to Override the Rule
The rule has real exceptions, and pretending otherwise is how heuristics get a bad name.
Override it upward when the replacement would be meaningfully worse. Older machines are sometimes heavier, more serviceable, and better built than what the same money buys now, and that is worth paying to keep.
Override it upward when the item is hard to replace, custom-sized, or part of a matched set where replacing one means replacing several.
Override it downward when the failure is a symptom rather than an event. A pump failure is an event. Rust through a cabinet, a cracked tub, a burned control board on a unit that has already had two boards, or a compressor on an old refrigerator all say the machine is ending, whatever the ratio says.
Also override downward for anything with a safety implication. A frayed cord, a cracked housing on a heat-producing appliance, or water reaching electronics is a replacement conversation, not a cost ratio.
Where the Rule Does Not Belong
The fifty percent rule is for durable goods with a replacement price. It does not apply to services, to consumables, or to anything whose value is not primarily the purchase price.
It also does not apply to structural or safety systems in a home. Roofing, wiring, plumbing, gas appliances, and anything load bearing are decided by condition, code, and a qualified inspection, not by a ratio.
And it does not apply to whether you should hire out household work. That decision is about time, skill, and risk rather than replacement cost. If you are weighing whether to keep doing everything yourself, comparing that against house cleaning services is a different calculation entirely.
FAQ
What is the fifty percent rule for repair or replace?
Replace an item when the total repair quote exceeds half of what an equivalent replacement costs today. Include diagnostic fees, delivery, and installation on both sides. Ignore what you originally paid, because that money is spent regardless of which choice you make.
How does age change the fifty percent rule?
Move the line down as the item ages. Use fifty percent in the first half of expected life, one third past the midpoint, and treat almost any major repair past three quarters of expected life as a replacement, because failures tend to cluster near the end of service life.
Should I include the diagnostic fee in the repair cost?
Yes, unless the shop credits it toward the work. On inexpensive items the diagnostic fee alone often pushes the ratio past the line, which is why paid repair rarely makes sense on anything that cost in the $40 to $100 range new.
Does the original purchase price matter?
No. What you paid is spent either way and has no bearing on which option is cheaper going forward. Including it is the most common reason people approve repairs they should have declined, because it feels like protecting an investment.
What is the expected lifespan of common appliances?
Washing machines and dishwashers commonly run ten to thirteen years, refrigerators twelve to fifteen, vacuums five to ten, and small kitchen appliances five to ten. Cordless tools are limited by battery packs, which typically last three to five years.
When should I ignore the fifty percent rule?
When the replacement would be clearly worse than what you have, when the item is custom or part of a matched set, when the failure signals general end-of-life rather than a single broken part, or when there is any safety concern such as a frayed cord or water reaching electronics.
Putting It to Work
Write the two numbers down, apply the age adjustment, and accept the answer. The rule is not perfect, but it is far better than the alternative, which is deciding based on how much the original purchase still stings.
If the deeper question is how much of the household workload you want to keep carrying yourself, that deserves a real number too. We are local, we price up front with no hidden fees, our crews are background checked, and booking happens online. Every home is different, so the real number depends on size, condition, and what you want covered. Get a quote and we will walk you through it.