Working out what size UPS you need has always been a bit of a headache. Spec sheets, VA ratings, watts, runtime charts… it's enough to make anyone reach for a calculator. So we built one.
Our new UPS runtime calculator and sizing tool does the maths for you. Tell it what you need to protect and how long it needs to keep running, and it'll point you to the right UPS in minutes.
What Size UPS Do I Need? Why Getting It Right Matters
Choosing a UPS isn't just about grabbing the biggest one you can afford. Get the size wrong, and you'll soon know about it:
- Too small: the UPS overloads, or the battery runs flat in seconds when the power drops.
- Too big: you've paid for capacity, and batteries, you'll never use.
Runtime matters just as much as size. A home office might only need five minutes to save work and shut down safely. A server room might need to keep running until the generator kicks in. Knowing both numbers is the key to picking the right UPS system. Want the bigger picture? Read our guide to UPS capabilities.
Meet the UPS Sizing & Runtime Calculator
Whether you're protecting a home office or a busy server room, our UPS sizing calculator takes the guesswork out of choosing a UPS. It saves you time, helps you avoid over-spending and gives you a solid starting point before you buy.
What You'll Need
- A list of the devices you want to protect, or their wattage (it's on the label or spec sheet)
- How long you need them to keep running during an outage
- Whether your site is single-phase or three-phase
What You'll Get
- A recommended UPS size
- An estimated runtime for your load
- Suggested UPS and battery options, from home and small office UPS systems to server and comms room UPS systems
How to Use the UPS Calculator in 3 Easy Steps
Getting your answer only takes a few minutes:
- Add your equipment. Enter each device you want to protect, or your total load in watts.
- Choose your runtime. Tell the calculator how long you need everything to keep running.
- Review your results. Check your recommended UPS size, then request a quote or have a chat with our team.
Top tip: include everything that needs backup, like servers, network switches, routers and monitors. Leave out laser printers and heaters, as they draw big bursts of power and usually aren't worth backing up.
Understanding Your UPS Sizing and Runtime Results
Numbers on a screen are one thing; knowing what they mean is another. Here's a quick explainer.
VA vs Watts in Plain English
UPS capacity is shown in two ways: VA (volt-amps) and watts. Watts are the power your equipment actually uses. VA is the total power the UPS has to supply to deliver it. They're related, but they're not the same, so always check both.
We recommend leaving around 20–25% headroom above your load. That way your UPS isn't running flat out, and you've got room to add more gear later.
Why Your Runtime Can Change Over Time
Runtime estimates assume healthy batteries, and batteries don't stay young forever. Most last 3–5 years, and heat, age and extra equipment all cut into runtime. Need more backup time? Battery cabinets or extended battery modules can stretch it.
Not sure how your current batteries are holding up? Book a battery health check, or find out more about UPS batteries.
When to Talk to a UPS Specialist
Our calculator is a great starting point, but some jobs need a bit more expert input. Give us a shout if you're dealing with:
- three-phase UPS systems or large loads
- data centres, hospitals or medical sites
- N+1 redundancy, often with modular UPS systems
- generator integration or long runtimes
- tight or hot equipment rooms
We'll happily double-check your results and book an obligation-free site assessment. Contact our team to get started.
Backed by 20+ Years of Sizing UPS Systems
We've sold and maintained more than 100,000 UPS systems over 20+ years, and our customers tell us our service is what sets us apart. This calculator packs that experience into a tool anyone can use, with our specialists across Australia, New Zealand and the Pacific Islands ready to help. Take a look at our projects.
Try the UPS Sizing & Runtime Calculator Today
Stop guessing and start sizing. Try the UPS sizing calculator now and find the right UPS in minutes. Prefer a chat? Request a quote or call us on 1300 555 992.