How do I compare products when their specifications describe capacity differently?
Quick answer
Don’t compare capacity numbers just because their labels look alike. For each exact product, copy the specification from current manufacturer documentation and record what it measures, its unit, and any stated conditions. Mark unclear or missing details, then ask the manufacturer to clarify before drawing a conclusion. Keep qualifications beside the figures; if their meanings or conditions are not comparable, leave the comparison unresolved. [S1] [S2]
The question, the details, the next step.
I’m comparing two products, but their specification sheets describe capacity differently. How do I start without assuming the numbers mean the same thing?
Treat each capacity figure as a separate claim to understand, not as a number that can automatically be compared with the other one. The FTC says comparative advertising should honestly inform consumers and identifies false or deceptive comparisons as a central concern. Its guidance also notes that context and omitted information can affect the impression a claim gives. [S1] [S2]
Open current manufacturer documentation for each exact product or model. Copy the capacity wording exactly, including its unit and any conditions or notes. Don’t silently convert, rename, or interpret a figure if the documentation doesn’t explain what it measures. Mark unknown details as “not stated” rather than filling in the gaps.
What should I record side by side, and how can I show gaps clearly?
Use this comparison table as a template, not as actual product information. Put the exact manufacturer wording next to your notes so it’s clear which details are documented and which still need verification:
| Field | Product A | Product B |
|---|---|---|
| Exact model | [model] | [model] |
| Capacity wording | [copy exactly] | [copy exactly] |
| What it measures | [manufacturer’s explanation / not stated] | [manufacturer’s explanation / not stated] |
| Unit | [copy exact unit / not stated] | [copy exact unit / not stated] |
| Stated conditions or method | [copy details / not stated] | [copy details / not stated] |
| Manufacturer document and date checked | [document; date] | [document; date] |
| Question to verify | [unresolved point] | [unresolved point] |
Keep qualifications beside the relevant figures, rather than separating them from the comparison. FTC guidance says qualifying information should be clear and close to the claim it qualifies. [S2] If a field is missing, show that plainly instead of leaving it blank or implying that the products match.
Suppose one listing gives a number and unit, while the other gives a capacity label but no conditions. Can I still say one holds more?
Not based on those details alone. You haven’t established whether the figures describe the same kind of capacity or use comparable conditions. The FTC guidance supports making the basis of a comparison clear, but it does not explain capacity labels, conversions, or how to judge manufacturers’ test methods. [S1] Don’t name a winner on this evidence.
Ask a focused question: “For model [exact model], what does [capacity wording] measure, in what unit, and under what stated conditions or method? Is it directly comparable with [other model’s exact wording]?” Ask for the relevant documentation or explanation. If the answer doesn’t resolve the question, note that the comparison remains unresolved and consider other verified features separately.
How should I use the comparison when deciding, without making the table look more certain than it is?
Separate documented facts from your conclusion. For example: “The manufacturers describe capacity differently; I haven’t confirmed that these figures measure the same thing, so I’m not treating them as directly comparable.” If documentation confirms a shared meaning, unit, and relevant conditions, you can compare on that stated basis and keep the qualification near the comparison. FTC guidance emphasizes truthful, substantiated claims and clear qualifying information. [S2]
The cited guidance does not establish how a particular product’s capacity is measured, whether two manufacturers use equivalent conditions, or whether a conversion is appropriate. Those details require product-specific documentation. A careful comparison can still show what you know—and what you need to verify—without implying that uncertainty has been resolved.
A practical checklist
Confirm the exact product and model before using a specification.
Copy each capacity statement exactly as the manufacturer presents it.
Record what the figure measures and its unit; write “not stated” when unclear.
Note stated conditions, method, qualifications, source, and date checked.
Ask the manufacturer about missing details and whether the figures are directly comparable.
Keep unresolved differences visible; don’t claim one product has more capacity without a clear basis.
A few more useful answers
Should I convert the units before comparing the products?
Only if you know what each figure measures and have established that the units refer to the same kind of quantity. The cited guidance gives no conversion rules, so verify the meaning and units in product-specific documentation first.
What if the manufacturer does not explain its capacity conditions?
Record the conditions as “not stated” and ask the manufacturer for clarification. If they remain unclear, treat the comparison as unresolved rather than assuming the conditions match.
Can I compare other product features while capacity is unclear?
Yes. Compare other features using their own documented descriptions, and keep the unresolved capacity issue separate so it does not imply a verified capacity advantage.
Sources
References used for this guide.
- [S1] FTC Statement of Policy Regarding Comparative Advertising ftc.gov · Checked
- [S2] FTC Advertising FAQs: Truthful Claims and Disclosures ftc.gov · Checked