How we research
Products
Every product on the site comes from a live Amazon listing retrieved through the Amazon product API. We record the ASIN, title, brand, price and photo exactly as returned, and read specifications only from what the listing states. Where the listing is silent on a spec, our spec sheets say "not stated". Prices change often, so treat the prices shown as a guide.
We do not test products hands-on. Picks are researched from published specifications, certifications and verified owner reviews, and tiered by who they suit rather than by a single score.
Formulas
- Dash cam recording time: card GB x 0.93 usable x 8,000 / total Mbps / 60, with typical bitrates of 12 Mbps (1080p), 16 (2K), 20 (2.5K), 32 (4K) and 10 Mbps per extra 1080p channel.
- Parking mode: battery Ah x condition x the state-of-charge difference between parking voltage and cutoff (plus 0.15V load sag), divided by camera watts / 12.4V / 0.9.
- Jump starter size: roughly one cranking amp per cubic inch for gas and two for diesel, scaled 0.75 to 1.8 for temperature. Products are matched on the engine size each maker states, with 15 percent margin.
- Tire inflation: tire volume from the sidewall size, air needed = volume x PSI rise / 14.7, divided by delivered flow of about 14, 22 or 38 liters per minute by inflator class.
- Tire pressure and temperature: the gas law on absolute pressure.
- Charge time: amp-hours to replace x 1.2 / charger amps.
These are estimates. Your camera, battery, engine and inflator will differ, which is why every calculator lets you change the inputs.
Before you rely on this: Researched from published specifications and verified owner reviews, not hands-on testing. General information, not professional advice; check your vehicle manual.