Most gear coverage begins with a product and works backwards to a verdict. We start from the standard or the physical constant and work forwards to a specification, because a specification stays true after the product it described has been discontinued.
This page sets out exactly how that is done, and what it does not include. If you find a number on this site whose origin you cannot trace after reading this, that is a fault in our work and we would like to hear about it: corrections@campgearexperts.com.
The four sources of every number we publish#
1. Published test standards. Where a property is governed by a standard, we use the standard and name it. ISO 23537 for sleeping bag ratings, ASTM F3340 for sleeping pad R-value, ISO 811 for hydrostatic head, ISO 11092 for evaporative resistance, ANSI/PLATO FL1 for lamp performance. Understanding what a standard actually measures, and what it deliberately excludes, is most of the value of reading it.
2. Physical constants. The specific heat capacity of water, the latent heat of fusion of ice, the vapour pressure of isobutane, the thermal conductivity of still air and of foam. These do not change and they settle a large share of camping questions on their own.
3. Declared specifications, described as such. Where we quote fill weights, denier, wall thicknesses or capacities, we give them as typical ranges across a category, and we say that is what they are. We do not treat a manufacturer figure as a measurement.
4. Explicit models built from the first three. Our calculators, and the charts on our guides, are models. Every one states its equation, its constants and its assumptions on the page where it appears, and every chart carries an expandable table of the numbers behind it. If you disagree with an assumption, you can see it and substitute your own.
What we do not do#
We do not run comparative laboratory testing of branded products, and we do not claim to. A credible thermal manikin programme, hydrostatic head rig or photometric sphere is a laboratory, not a website, and pretending otherwise is one of the more common forms of dishonesty in this field.
We also do not accept free products in exchange for coverage, run sponsored posts, or write to a retailer's category structure. See our disclosure page for the commercial arrangements that do exist.
Because we do not run product tests, we do not publish "best of" rankings. That is a deliberate limit, not an oversight. Our answer to "which one should I buy" is a specification and a decision rule that you can apply to whatever is available where you are.
Protocols you can run yourself#
The other half of the method is giving you tests you can actually perform, because a measurement you took beats a review you read. Several guides include one:
- The two-thermometer method for finding your personal offset from a sleeping bag rating, on sleeping bag temperature ratings
- Weighing a gas canister before and after a trip to calibrate your own fuel consumption, on how much stove fuel to carry
- The sink test that distinguishes a shell that is wetting out from one that is genuinely leaking, on reproofing rain gear
- The loft check before and after washing a down bag, on washing down gear
These are designed around domestic equipment: a kitchen scale, two thermometers, a bath, a tape measure.
How our models are bounded#
Every model has a range in which it is useful and a range in which it is not. We state both.
The sleep system calculator, for example, is reliable for relative comparisons and rough for absolute ones, because individual thermal comfort varies by several degrees between people of similar size. The cooler model uses steady state conduction and ignores lid seal quality, so its answer is a floor rather than a prediction. The fuel model assumes a delivered efficiency band for each stove type, which is why the page tells you how to calibrate it against your own equipment in three trips.
Where a model would need to be so hedged that it stopped being useful, we do not publish it.
Review and updating#
Pages carry a visible last reviewed date. A review means the standards cited were checked as current, the arithmetic was re-run against the constants in our data files, and internal links were verified. Where a figure changed, the change is logged on the corrections page with the date and the reason.
Charts and datasets are generated from source data at build time rather than drawn by hand, which means a corrected constant propagates to every page, chart and downloadable table that uses it in the same update. Every figure we compute is collected on the reference data page, with a CSV of the exact numbers plotted, so anyone can reproduce or challenge it.
Conflicts we are aware of#
The main structural pressure on any site in this field is towards recommending products, because that is where the money usually is. We have chosen a format that does not depend on it, and the editorial standards page sets out the rules that keep it that way. The second pressure is towards certainty, because confident writing performs better than honest writing. Where the evidence is thin, we say so on the page rather than rounding it to a recommendation.