Generator Sizing Calculator
Work out the generator size in kVA and kW for a given load, allowing for power factor, starting surge from motors and air conditioners, and headroom for growth.
Open calculatorFree tools
Tools
Calculators and checkers we built for our own jobs, free for anyone to use. No sign up, no limits, nothing stored.
Built for our own jobs
Free tools, no sign up
We built these for survey work, quotes and troubleshooting on real installations. They are free to use and there is nothing to register for. The calculators run entirely in your browser, so what you type never reaches our server.
Power and energy
Cable Size & Voltage Drop Calculator
Pick the right cable cross section in square millimetres for a given current and run length, and check the voltage drop stays inside the three percent limit.
Open calculatorSolar & Battery Sizing Calculator
Size a solar system from your daily energy use: panel wattage, battery bank capacity, inverter rating and the days of autonomy you want to cover.
Open calculatorGenerator Subscription Cost Calculator
Convert a neighbourhood generator subscription in amperes into kilowatt hours and a monthly cost, so you can see what each appliance is really adding to the bill.
Open calculatorUPS Runtime Calculator
Estimate how long a UPS will carry your load from the battery capacity, voltage, load in watts and the efficiency of the inverter.
Open calculatorCCTV and surveillance
CCTV Storage Calculator
Size the hard drive for a camera system from the number of cameras, resolution, frame rate, codec and how many days of footage you need to keep.
Open calculatorCCTV Lens & Field of View Calculator
Work out what a camera actually sees: the field of view, coverage width and angle for a given lens focal length, sensor size and distance to the subject.
Open calculatorCCTV Pixel Density Calculator
Check whether a camera gives enough pixels per metre to detect, recognise or identify a person at a given distance, using the EN 62676 standard.
Open calculatorPoE Power Budget Calculator
Check how many cameras or access points a PoE switch can really carry, allowing for cable losses, PoE standards and sensible headroom.
Open calculatorFiber and network
Fiber Loss Budget Calculator
Work out the total optical loss on a fiber link from cable length, splices, connectors and splitters, then compare it against your power budget.
Open calculatordBm, mW & dB Converter
Convert optical and RF power between dBm and milliwatts, and work out gain or loss in dB between two power levels.
Open calculatorFiber Optic Colour Code Chart
The TIA 598 colour code for fiber strands, buffer tubes and ribbons, with the twelve colour sequence and how to find any strand number in a cable.
Run the checkIP Subnet Calculator
Turn an IPv4 address and prefix into the network address, broadcast, usable host range, mask, wildcard and host count.
Open calculatorVLSM Subnet Divider
Split a network into smaller subnets of the sizes you actually need, and get the ranges, masks and usable hosts for each one without overlaps.
Open calculatorWi-Fi Channel Planner
Which Wi-Fi channels do not overlap on 2.4 GHz and 5 GHz, how wide to set the channel, and how to lay out access points so they stop interfering with each other.
Run the checkFresnel Zone & Link Calculator
Work out the Fresnel zone radius, required antenna height and free space path loss for a point to point wireless link, including earth curvature over long spans.
Open calculatorRJ45 Pinout & Cable Reference
The T568A and T568B wiring order for RJ45 connectors, straight through against crossover, and the maximum run length and speed for each cable category.
Run the checkBandwidth & Transfer Time Calculator
Convert between bits and bytes, work out how long a transfer takes at a given speed, and size a connection for a number of users.
Open calculatorHosting and sysadmin
SLA Uptime Calculator
Turn an uptime percentage into the downtime it actually allows per day, week, month and year, and compare the common SLA tiers side by side.
Open calculatorRAID Capacity Calculator
Work out the usable capacity, fault tolerance and rebuild risk of a RAID array for every common level, from RAID 0 through RAID 6 and RAID 10.
Open calculatorCron Expression Builder
Build a cron schedule from plain settings and read any existing cron expression back in plain English, with the next run times worked out for you.
Open calculatorhtaccess Redirect Generator
Generate the htaccess rules for 301 redirects, forcing HTTPS, adding or removing www, and keeping old URLs working after a website migration.
Open calculatorPassword Generator & Strength Checker
Generate strong random passwords in your browser and check how long a password would take to crack, measured properly in bits of entropy.
Open calculatorHash & Encoding Tool
Generate MD5, SHA 1, SHA 256 and SHA 512 hashes, and encode or decode Base64 and URL text, entirely inside your own browser.
Open calculatorDomain and email checks
DNS Lookup
Look up the live DNS records for any domain, including A, AAAA, MX, NS, TXT, CNAME and SOA, straight from the authoritative answer.
Run the checkDomain Registration Lookup
Look up who a domain is registered with, when it was created, when it expires and which nameservers it uses, through the modern RDAP service.
Run the checkSSL Certificate Checker
Check the SSL certificate on any website: who issued it, which names it covers, when it expires and how many days are left.
Run the checkSPF, DKIM & DMARC Checker
Check whether a domain has valid SPF, DKIM and DMARC records set up, which is usually why business email lands in the spam folder.
Run the checkBlacklist (RBL) Checker
Check whether a mail server IP address is listed on the major spam blacklists, which is the usual reason outgoing email is rejected or silently dropped.
Run the checkWhat Is My IP Address
Show the public IP address, browser and connection details your network is presenting to the websites you visit.
Run the check