Buying guides
What things actually cost per unit — per diaper, per quart, per ml, per page. We do the math so you compare true value, not pack size.
Best Diapers for Newborns (2026): What Actually Matters, and the Cheapest That Deliver
The "best" newborn diaper is the one that fits, doesn't leak, and doesn't blow your budget on 300 changes a month. Here is what actually separates a good newborn diaper from a bad one — and the cheapest options by real cost per diaper.
Starter 5 min· updated 7/19/2026
Cheapest Dog Food Per Pound: Every Brand Ranked (2026)
The cheapest dog food per pound we track is Kibbles 'n Bits at about $0.88/lb in a 31 lb bag. Every dry dog food ranked by real cost per lb — from $0.88 to $14.99 — plus the 40 lb bag math and the one caveat at the top of the chart.
Shopping 6 min· updated 7/19/2026
Diaper Cost Comparison by Size: What Each Size Really Costs Per Diaper
Diaper cost climbs with size — the same Huggies line runs ~$0.37 per diaper in Size 4, ~$0.43 in Size 5, and ~$0.62 in Size 7. A size-by-size cost table from real tracked prices, brand tiers, and the subscribe-vs-one-time math.
Shopping 6 min· updated 7/19/2026
How Long Does a Propane Tank Last? Grill Hours by BTU, and How to Check
A standard 20-lb grill tank lasts about 14–20 hours of grilling — roughly 1–2 weeks for most people. Here is the burn time by appliance and BTU, how to tell how much is left, and the cost per hour.
Shopping 5 min· updated 7/18/2026
How Often to Change Your Furnace / HVAC Air Filter — and What a Year Costs
Change a 1-inch furnace or AC filter every 1–3 months, a 4-inch media filter every 6–12. Pets, allergies and constant running shorten that. Here is the interval by filter type, what happens if you skip it, and the real cost per year.
Shopping 5 min· updated 7/18/2026
How Long Does a Bar of Soap Last? Per Bar, and How to Make It Last Longer
A bar of soap lasts one person about 3–4 weeks of daily body washing — but keeping it dry between uses can nearly double that. Here is the real math by bar size and use, the cost per wash, and why bars outlast body wash per dollar.
Shopping 5 min· updated 7/17/2026
Bar Soap vs Body Wash: Cheaper, Cleaner, Better for Skin?
Bar soap almost always wins on cost per wash and packaging; body wash wins on feel, dry skin, and dose control. Here is how they really compare on price, cleaning, hygiene and the environment — with the real cost per fluid ounce we track.
Shopping 5 min· updated 7/15/2026
Dishwasher Pods vs Powder vs Gel: Which Cleans Best, and Which Is Cheapest
Pods are the most convenient and usually clean best; powder is the cheapest per load and lets you adjust the dose; gel is the weakest. Here is how the three compare on cleaning, cost per load and hard water — with the real per-pod price we track.
Shopping 5 min· updated 7/15/2026
How Long Does a Tube of Toothpaste Last? By Size, Per Person, and Per Cent
A standard tube lasts about a month per person at the dentist-recommended pea-sized dose — but most people use far more and burn through it in half the time. Here is the real math by tube size, plus the cost per brushing from live prices.
Shopping 5 min· updated 7/15/2026
How Long Does Body Wash Last? Per Bottle in Use, and On the Shelf
A standard bottle of body wash lasts about a month of daily showers per person — but a loofah, the amount you use, and whether you have a shelf-life question all change the answer. Here is the real math, plus the cost per shower.
Shopping 5 min· updated 7/15/2026
How Long Does Deodorant Last? On Your Skin, In the Stick, and On the Shelf
Three different "how long" questions get mixed up here: how many hours a swipe protects, how many months a stick lasts, and how long it keeps before it expires. Here are real answers to all three — plus the cost per day, from live prices.
Shopping 5 min· updated 7/15/2026
How Long Does Sunscreen Last? Shelf Life, After Opening, and Per Bottle
Sunscreen is an FDA-regulated drug required to stay effective for at least three years — but heat, an open cap, and under-using a bottle all change the real answer. Here is how long it lasts on the shelf, once opened, and per application.
Shopping 5 min· updated 7/15/2026
How Much Coffee Per Cup? The Right Ratio by Method — and the Real Cost Per Cup
The standard is about 1 to 2 tablespoons of ground coffee per 6-ounce cup, but the right amount depends on your brew method and taste. Here is the ratio by method, the gram math, and what a cup actually costs by grounds, pods and K-Cups.
Shopping 5 min· updated 7/15/2026
How Much Conditioner to Use: Where to Put It, How Much, and Cost Per Use
Conditioner goes on the opposite half of your hair from shampoo — the lengths and ends, never the scalp. Here is how much to use by hair length, how to apply it, and the real cost per use from live prices.
Shopping 5 min· updated 7/15/2026
How Much Protein Is in a Protein Bar? Typical Grams, and the Cost Per Gram of Protein
Most protein bars pack 10–20 grams of protein — but the number on the front tells you nothing about value. What matters is cost per gram of protein, and here is how to work it out, plus the real price-per-bar spread from live listings.
Shopping 5 min· updated 7/15/2026
How Much Shampoo to Use: By Hair Length, and the Real Cost Per Wash
The right amount of shampoo is far less than most people squeeze out — from a nickel for short hair to two quarters for long hair. Here is the amount by hair length, how long a bottle should last, and the real cost per wash from live prices.
Shopping 5 min· updated 7/15/2026
How Much Sunscreen to Use: The Shot-Glass Rule (and Why Most People Under-Apply)
Almost everyone uses too little sunscreen, which is why a "30 SPF" often protects like a 10. Here is exactly how much to apply — by body and by face — how often to reapply, and how to buy it so applying enough doesn't feel expensive.
Shopping 5 min· updated 7/15/2026
How Much to Feed a Dog by Weight: The Daily Chart, and What It Costs Per Day
How much dry food a dog needs depends mostly on its adult weight — roughly 1/3 cup a day for a 10-pound dog up to 4+ cups for a 100-pound dog. Here is the full chart, the factors that shift it, and the real cost per day from live prices.
Shopping 5 min· updated 7/15/2026
How Often Should You Replace a Loofah? (Sooner Than You Think)
A loofah is a warm, damp, bacteria-friendly sponge, and most people keep theirs far too long. Here is how often to replace a natural vs plastic loofah, how to make one last, and the cheaper, more hygienic alternatives.
Shopping 5 min· updated 7/15/2026
How Often Should You Replace Razor Blades? Shaves Per Blade, and the Cost Per Shave
Most cartridge and safety-razor blades are good for 5–10 shaves — not a set number of days. Here is how to know when a blade is done, and the real cost per shave once you work it out from the price per cartridge.
Shopping 5 min· updated 7/15/2026
How Often Should You Replace Your Toothbrush? Every 3–4 Months, and the Signs
Dentists say every three to four months — but frayed bristles, a cold, and how hard you brush can all mean sooner. Here is when to replace a manual or electric brush, why it matters, and what a year of brushes actually costs.
Shopping 5 min· updated 7/15/2026
Liquid vs Powder Laundry Detergent: Which Cleans Better, and Which Is Cheaper
Powder is usually the cheapest per load and great on ground-in dirt; liquid is better for grease and pre-treating stains and dissolves in cold water. Here is how they really compare on cost, cleaning, storage and hard water — with the real cost per load we track.
Shopping 5 min· updated 7/15/2026
SPF 30 vs 50: The Real Difference (It’s Smaller Than the Number Suggests)
SPF 30 blocks about 97% of UVB rays; SPF 50 blocks about 98%. The jump in the number is far bigger than the jump in protection. Here is what SPF actually measures, when 50 is worth it, and why how much you apply matters more than 30 vs 50.
Shopping 5 min· updated 7/15/2026
Best Cat Litter by Type (2026): Clumping vs Crystal vs Lightweight, and the Cheapest of Each
There is no single "best" cat litter — there's the best type for your setup, then the cheapest good option within it. Here is how clumping clay, crystal, and lightweight actually differ, and the real cost per pound of each.
Starter 5 min· updated 7/14/2026
How Many Diapers Does a Newborn Use? (Per Day, Per Week, and What It Costs)
A newborn goes through 8–12 diapers a day — about 300 in the first month alone. Here is the real count by age, how many boxes to buy before the baby arrives, and exactly what it costs at today's prices.
Starter 5 min· updated 7/14/2026
How Much Laundry Detergent to Use (And Why Using Less Saves Real Money)
Most people use 2–4× more laundry detergent than they need. Here is the right dose by load size, water hardness, and format — plus the part nobody mentions: overdosing quietly doubles your cost per wash and leaves residue that greys your clothes.
Starter 5 min· updated 7/14/2026
How Often to Change Your Oil (Forget the 3,000-Mile Myth)
The 3,000-mile oil change is a marketing relic. Modern synthetic oil and modern engines go 7,500–15,000 miles between changes. Here is the real interval by oil type and driving style — and the honest math on what an oil change actually costs per year.
Starter 5 min· updated 7/14/2026
What Does 5W-30 Mean? The Numbers Decoded (And Why They Don't Change the Price)
5W-30 is a viscosity grade, not a quality grade: the 5W is how the oil flows when cold, the 30 is how thick it stays when hot. Here is what each number actually measures — and the part nobody mentions: the grade barely moves the price per quart.
Starter 5 min· updated 7/13/2026
How Long Does Synthetic Oil Last? Miles, Months, and Cost Per Year
Full synthetic oil lasts about 7,500–10,000 miles or 6–12 months between changes — roughly twice as long as conventional. At the ~$6.40 per quart we track, a typical 5-quart car costs about $50–$65 a year in oil.
Shopping 6 min· updated 7/11/2026
HP Instant Ink vs Buying Cartridges: Which Is Cheaper Per Page?
Ink subscriptions like HP Instant Ink charge per page, not per cartridge — roughly $0.02–$0.10 per page depending on plan. That beats most standard cartridges but loses to high-yield ink and laser toner. Here's the honest break-even.
Shopping 6 min· updated 7/11/2026
5W-20 vs 5W-30: Cost Per Quart and Which Your Engine Wants
5W-20 and 5W-30 cost almost exactly the same per quart — across the synthetic oil we track both land around $6.39 per quart at the median. So the choice is your engine's spec, not the price. Here's the honest math.
Shopping 5 min· updated 7/10/2026
Cheapest Cat Food: Real Cost Per Pound
Dry cat food runs from about $0.89 to $4.29 per pound — a near-5x spread on the same shelf. Ranked by real cost per lb: the cheapest big bags, the small-bag penalty, and why wet food breaks the comparison.
Shopping 6 min· updated 7/10/2026
Cheapest Size 5 Diapers by Real Cost Per Diaper
Size 5 boxes range from about $0.25 to $0.80 per diaper — a 3x spread for the same size on the same shelf. Ranked by real cost per diaper: the cheapest brands, the small-box trap, and the yearly math.
Shopping 6 min· updated 7/10/2026
Diaper Cost Per Diaper: The Cheapest Brands by Real Unit Price
A newborn goes through 8–12 diapers a day, so a few cents per diaper is real money. Ranked by true cost per diaper, store and value brands beat premium ones by nearly 4x — the data, and the traps.
Shopping 6 min· updated 7/10/2026
Dog Food Cost Per Pound: Big Bags, Boutique, and the Air-Dried Caveat
Dry dog food ranges from under $1 to about $15 per pound. Ranked by real cost per lb, big bags of mainstream kibble win — but there is one honest caveat worth understanding first.
Shopping 6 min· updated 7/10/2026
Eau de Parfum vs Eau de Toilette: Cost Per Wear, Not Per Bottle
Eau de parfum costs a little more per ml but is more concentrated, so you spray less — which is why the honest comparison is cost per wear, not the sticker price. Across the fragrance we track, EDP runs about $0.23–$4.15 per ml and EDT about $0.14–$1.38.
Shopping 5 min· updated 7/10/2026
Fragrance Cost Per ml: Designer, Niche, and the Bottle-Size Trick
A 30x gap separates the cheapest and priciest fragrances per millilitre, and bottle size plays as big a role as the brand. Ranked by real cost per ml, here is how to read a fragrance shelf.
Shopping 5 min· updated 7/10/2026
How Much Do Diapers Cost Per Month? The Real Math by Age and Brand
Diapers cost roughly $30 to $240 a month depending on age and brand tier — most families land around $60–$100. The month-by-month math from real tracked per-diaper prices, a stage table, and the honest first-year total.
Shopping 6 min· updated 7/10/2026
Laser vs Inkjet: The Real Cost Per Page
Toner looks expensive and ink looks cheap — until you divide by pages. Across the cartridges we track, toner runs about $0.023–$0.063 per page while inkjet spans $0.010–$0.41. Here is the honest break-even math.
Shopping 6 min· updated 7/10/2026
Motor Oil Cost Per Quart: Why the 5-Quart Jug Wins
Motor oil is sold in quarts and litres, blends and full synthetics, jugs and single bottles — which makes the sticker price useless. Ranked by real cost per quart, the pattern is clear.
Shopping 6 min· updated 7/10/2026
Printer Ink Cost Per Page: Ink vs Toner, and Which Cartridges Cost Less
The sticker price on a cartridge tells you almost nothing. Ranked by real cost per page, the cartridges we track run from about a penny a page (high-yield ink and laser toner) to about $0.41 — roughly a 40x spread. Here is the data.
Shopping 6 min· updated 7/10/2026
Printers With the Cheapest Ink: Every Ink System Ranked by Cost Per Page
A printer is a subscription to its cartridge family. Every ink system we track ranked by real cost per page — from Brother's ~$0.010 super-high-yield ink to Canon's ~$0.41 small cartridges — plus the break-even math for paying more up front.
Shopping 7 min· updated 7/10/2026
Razor Blades Cost Per Cartridge: The Real Price of a Shave
The razor handle is nearly free — the blades are the lifetime cost. Ranked by real cost per cartridge, store-brand and subscription blades beat name brands by up to 8x.
Shopping 5 min· updated 7/10/2026
Shampoo Cost Per Fl Oz: Bulk vs Boutique
The same amount of shampoo can cost 16 cents or over 2.50 dollars per fluid ounce. Ranked by real cost per fl oz, bottle size and brand tier explain almost the entire gap.
Shopping 5 min· updated 7/10/2026
Skincare Cost Per ml: How to Spot the Markup
The same active ingredient can cost 6 cents or 2 dollars per millilitre depending mostly on the jar it comes in. Ranked by real cost per ml, here is where the money actually goes.
Shopping 6 min· updated 7/10/2026