All Calculators — FocalMath

Five calculators, each solving a real problem instead of displaying a static table. All five run entirely client-side, none require an account, and every result is URL-encoded so you can bookmark or share a specific answer rather than losing it the moment you close the tab.

The Depth of Field & Hyperfocal Calculator is the flagship — enter your sensor format, focal length, aperture and subject distance and get near/far sharp limits, total depth of field, and the hyperfocal distance, with a to-scale visual band showing where the sharp zone actually sits. The Exposure Triangle Solver locks any two of ISO, aperture and shutter speed and solves the third when you change one of them, so you can answer "if I stop down two stops, what shutter speed keeps the same exposure" without doing stop arithmetic by hand. The Astro 500/NPF Rule Calculator gives you the traditional 500-rule estimate and the more accurate NPF-rule estimate side by side, accounting for your camera's real pixel pitch and the target's declination. The Crop-Factor & Equivalence Converter translates a lens on one sensor format into its field-of-view and depth-of-field equivalent on another — kept deliberately separate, since conflating them is the single most common mistake in this corner of photography. The Print Size / DPI Calculator turns a megapixel count into the largest comfortable print at a chosen viewing distance.

Each tool page has a full explanation beneath the calculator covering how the numbers are derived and how to read the result — not just the widget on its own. If you want the deeper reasoning behind any of these calculations rather than just the result, the guides section covers each concept in full.

All five calculators are also linked to the site's reference layer where it's genuinely useful — the DoF calculator can be checked against a specific camera's real sensor format, the astro calculator uses a camera's real pixel pitch when you look it up on its own reference page, and the crop-factor converter draws on the same 17-format sensor data used throughout the rest of the site. None of the five requires you to install anything or create an account.