About RepLock
RepLock is a free, independently run site built around six calculators and reference guides for home and business security — keypad codes, camera storage and coverage, password strength, lock grades, and safe ratings. There’s no company behind it beyond the person who built and maintains it, and it’s supported by advertising rather than subscriptions or lead generation.
How the tools compute their numbers
The Keypad Combination Calculator is straight combinatorics: given a code length and the number of keys on the pad, it works out how many distinct codes exist (with or without repeated digits allowed), then divides that count by an attempt rate you set — including any lockout delay the keypad enforces after a run of wrong tries — to estimate a worst-case brute-force time.
The Security Camera Storage Calculator starts from resolution and frame rate to estimate a bitrate per camera, multiplies that by recording hours per day, retention days, and camera count, and converts the result to GB and TB, rounding up to a suggested drive size. It’s an estimate: real footage varies with compression, scene motion, and codec (H.264 vs H.265), so it is meant for sizing a drive with headroom, not a guaranteed figure.
The Password Entropy Calculator computes entropy in bits as log2(pool size ^ length), where pool size is the count of character classes you say the password draws from (lowercase, uppercase, digits, symbols). It then divides the total possible combinations by a guesses-per-second figure you choose to estimate an offline crack time. This measures theoretical keyspace, not whether a specific password appears in a leaked-password list.
The Camera Lens Coverage Calculator uses actual optics: horizontal field of view is derived from a camera’s focal length and sensor width (2 × atan(sensor width ÷ (2 × focal length))), and the width of the scene captured at a given distance follows from that angle — no lookup tables, just the trigonometry a lens actually obeys.
The Lock Grade Guide (ANSI/BHMA) and the Safe Rating Guide (UL Fire & Burglary) aren’t calculators — they’re reference tables. The lock guide lays out what ANSI/BHMA Grade 1, 2, and 3 actually require: the cycle counts and forced-entry strike tests a deadbolt or lockset has to survive to earn each grade. The safe guide does the same for UL ratings — the Class 350, 150, and 125 fire ratings (by temperature and duration protected) and the RSC, TL-15, TL-30, and TL-30x6 burglary ratings (by tool-resistance time) — so you can filter by what you actually need: fire protection, burglary protection, or both.
Anyone curious about the older end of all this can visit the Museum of Locks & Security, a separate section walking through the history of keys, padlocks, vaults, and alarms, built from Wikipedia and Wikimedia Commons entries rather than original research.
What this is and isn’t
RepLock is not affiliated with ANSI, BHMA, UL, Wikipedia, or any lock, camera, alarm, or safe manufacturer — the standards and ratings referenced here are used for identification and comparison only. The calculators produce estimates from the numbers you enter and the assumptions described above; they are not a security audit, and they don’t know your building, your threat model, or local code. This is general informational content, not professional security, locksmith, or safety advice — for decisions about protecting a specific property, talk to a licensed locksmith or a qualified security professional.
Questions, corrections, or a tool idea? See the contact page.