How to choose a firewall for your office
Users, internet speed, VPN and licences: the five questions that decide which firewall model you need, and what to ask sellers.
Updated 26 Oct 2026
A firewall sits between your office network and the internet. Pick one that is too small and the internet slows down the moment you switch on security features; pick one that is too big and you pay for capacity you never use. These five questions get you to the right size.
1. How many people and devices?
Count users, not just computers. Most staff have a laptop and a phone on the network, plus printers, cameras and guest Wi-Fi. As a rough guide, small offices of up to 25 users suit entry desktop models, 25 to 100 users suit mid-range desktop or 1U models, and above that you are into rack-mounted appliances.
2. How fast is your internet line?
Look at the threat protection or NGFW throughput figure on the datasheet, not the headline firewall throughput. The headline number is measured with security features switched off. Your threat protection throughput should be comfortably above your internet line speed, with room for the next upgrade.
3. Do people work from home or from branches?
If staff connect from home, check the number of SSL VPN or IPsec users the model supports. For branches, ask about SD-WAN, which lets one firewall use two internet lines and fail over automatically.
4. What licence do you need?
Almost every next-generation firewall needs a yearly security subscription for web filtering, antivirus and intrusion prevention. Ask every seller to quote the same licence bundle and the same number of years, otherwise the prices are not comparable. Renewal prices matter as much as the first-year price.
5. Who will install and support it?
A firewall is only as good as its configuration. Ask whether the quote includes installation, policy setup, and support after go-live, and whether the seller is an authorised partner of the brand.
What to send sellers
- Number of users and sites
- Internet line speed, and whether you have two lines
- Remote users or branch VPN needed
- Licence term you want (1, 3 or 5 years)
- Whether you need installation and AMC
Use the free firewall sizing tool on this site to see which models fit, then post one requirement to get comparable quotes.