Stop estimating. Here is the exact formula to calculate your VoIP savings, with every variable explained and real UK benchmarks provided.
The Formula
Monthly Savings = (Current Per-User Cost - VoIP Per-User Cost) × Number of Users
Annual Savings = Monthly Savings × 12
Break-Even (months) = One-Time Costs ÷ Monthly Savings
3-Year ROI = ((Annual Savings × 3) - One-Time Costs) ÷ One-Time Costs × 100%
Step 1: Calculate Your Current Per-User Cost
Add up ALL your monthly telecom costs and divide by phone users:
| Cost Item | Your Amount | UK Average |
|---|---|---|
| Line rental / PRI charges | £_____ | £28/user |
| Maintenance contract | £_____ | £8/user |
| Feature licenses (recording, VM, etc.) | £_____ | £9/user |
| Long distance charges | £_____ | £5/user |
| IT admin time (hours × rate) | £_____ | £6/user |
| Hardware lease payments | £_____ | £4/user |
| Total ÷ Users = | £_____ | £60/user |
UK average from our 500-company dataset: £60 per user per month.
Step 2: Calculate VoIP Cost
DialPhone standard plan: £24 per user per month. Everything included.
Step 3: Calculate Savings
| Your Company Size | Current (at £60/user) | VoIP (at £24/user) | Monthly Savings | Annual Savings |
|---|---|---|---|---|
| 10 users | £600 | £240 | £360 | £4,320 |
| 25 users | £1,500 | £600 | £900 | £10,800 |
| 50 users | £3,000 | £1,200 | £1,800 | £21,600 |
| 100 users | £6,000 | £2,400 | £3,600 | £43,200 |
Step 4: Calculate Break-Even
| One-Time Cost | Amount |
|---|---|
| Desk phones (40% of users × £130) | £_____ |
| Headsets (60% of users × £60) | £_____ |
| Implementation | £0 (DialPhone includes this) |
| Number porting | £0 (DialPhone includes this) |
| Training | £0 (DialPhone includes this) |
| Total one-time | £_____ |
For 50 users: 20 phones (£2,600) + 30 headsets (£1,800) = £4,400
Break-even: £4,400 ÷ £1,800/month = 2.4 months
Step 5: Calculate 3-Year ROI
For 50 users:
3-Year Savings: £21,600 × 3 = £64,800
Minus One-Time: £64,800 - £4,400 = £60,400 net savings
ROI: £60,400 ÷ £4,400 × 100% = 1,373% ROI
Sensitivity Check
What if your current cost is lower than average?
| Your Per-User Cost | Monthly Savings (50 users) | Break-Even |
|---|---|---|
| £60 (UK average) | £1,800 | 2.4 months |
| £45 (below average) | £1,050 | 4.2 months |
| £35 (already efficient) | £550 | 8.0 months |
| £24 (already on VoIP) | £0 | N/A |
Even at £35/user (well below average), VoIP saves money within 8 months.
At £24/user, you are already on competitive VoIP — compare features and support quality instead of price.
For a personalised calculation using your actual invoices, visit DialPhone for a free bill analysis.
