| FortiGate Firewall Sizing Guide: How to Choose the Right Model for Your Business |
“## Why Sizing Mistakes Are So Common
The most frequent firewall-buying mistake isn’t choosing the wrong vendor — it’s choosing the wrong size. Businesses often size a firewall by user count alone, then find performance drops sharply once SSL inspection, IPS and application control are all switched on simultaneously, because a firewall’s real-world throughput with full security enabled is meaningfully lower than its raw, uninspected throughput number.
The Factors That Actually Matter
- Concurrent users, not total employees. A 200-person office where 60 are usually connected at once sizes differently from one where all 200 are online simultaneously.
- How much traffic is encrypted. Since most web traffic is HTTPS today, budget for SSL inspection throughput specifically, not just general firewall throughput.
- Which security profiles you’ll actually enable. IPS, antivirus, web filtering and application control each add inspection overhead — size for the profile combination you intend to run in production, not the base firewall-only figure.
- VPN and SD-WAN load. Site-to-site VPN tunnels and SD-WAN link monitoring both consume processing capacity, particularly at branch sites running multiple WAN links.
- Growth headroom. Sizing exactly to today’s traffic often means a forced upgrade within two to three years; most organisations size with meaningful headroom for growth.
A Rough Framework by Site Type
- Home office / micro-branch (under 25 users): entry-level desktop models
- Small office (25–80 users): compact branch firewalls with SD-WAN built in
- Mid-sized branch or office (80–250 users): mid-tier branch appliances with higher port density
- Regional office or small data centre (250–1000+ users): higher-throughput mid-range to enterprise appliances
These bands are a starting point, not a substitute for sizing against your actual traffic profile.
Don’t Forget Licensing
The appliance is only part of the cost. FortiGuard security subscriptions (IPS, antivirus, web filtering, application control) are licensed separately and typically renew annually — factor ongoing subscription cost into your total cost of ownership, not just the upfront hardware price.
The Safest Way to Size Correctly
Vendor datasheet throughput numbers are measured under specific lab conditions that rarely match a live network. The most reliable approach is to share your actual environment — user count, site count, current bandwidth usage and which security features you plan to enable — with a partner who can size against real-world conditions rather than headline numbers.
Frequently Asked Questions
Should I just buy the biggest model I can afford?
Not necessarily — oversizing wastes budget on capacity you won’t use for years, and licensing costs typically scale with the appliance tier too. Right-sizing with growth headroom is usually more cost-effective than maximum sizing.
Does SSL inspection really make that much difference to performance?
Yes, often significantly — decrypting and re-encrypting traffic for inspection is computationally expensive, which is exactly why Fortinet builds dedicated security processors into its appliances to keep this fast.
Can I resize later if I get it wrong?
You can upgrade to a larger appliance, but that means new hardware and, often, a licence transfer — getting the sizing right upfront avoids an unplanned early replacement.
Can MetaPoint Technologies size a FortiGate for my specific environment?
Yes — MetaPoint Technologies’s pre-sales team sizes FortiGate models against your real user count, traffic and security profile requirements. WhatsApp +91 99895 44438 to start.
Get a Sizing Recommendation
MetaPoint Technologies is an authorised Fortinet partner across Hyderabad, Telangana, Andhra Pradesh and Karnataka. Share your environment details with our pre-sales team and we’ll recommend the right FortiGate model and licensing tier. Call or WhatsApp +91 99895 44438.”
