A – Phone on contract
–Total cost over the horizon
Average per month: –
| Item | Amount |
|---|
with bonus, if the conditions are met:
Remaining instalments after the horizon (not in the total):
Credits after the horizon (not counted):
Phone Contract vs SIM-Only Calculator
Should you take the phone with a contract, buy the same handset outright and add a SIM-only plan, or keep your current phone and pay only for a SIM-only plan? This calculator puts the three paths side by side and shows what each really costs over 12, 24 or 36 months. It works only with the figures you enter: prices, promotional phases, one-off fees, separately billed device instalments and credits.
Your result
–
The device names for A and B differ — check that you are really comparing the same handset.
B – Handset outright + SIM-only
–Total cost over the horizon
Average per month: –
| Item | Amount |
|---|
with bonus, if the conditions are met:
Remaining instalments after the horizon (not in the total):
Credits after the horizon (not counted):
C – Keep current phone
An additional option — not ranked as equivalent to a new handset.
–Total cost over the horizon
Average per month: –
| Item | Amount |
|---|
with bonus, if the conditions are met:
Remaining instalments after the horizon (not in the total):
Credits after the horizon (not counted):
Extra spend for a new device versus carrying on:
versus A: –
versus B: –
The average per month is rounded; average × months can differ from the total by a few cents — the total is the figure that counts.
How this calculator works
For each path the calculator adds up the pure cash outlay over the chosen horizon. One-off costs (the handset payment or purchase price, the activation fee and shipping) are paid at the start. The monthly price is summed phase by phase from month one; a promotional price for the first few months is simply its own phase. Only months inside the horizon count.
For the time after the last price period, exactly what you choose applies: the later monthly price is not yet known (then the path has no total, only the known months), the monthly price stays the same, or a different monthly price applies with an optional one-off fee. The calculator never lowers a price on its own.
A device instalment is only included if it is billed separately from the monthly price; it runs over its own term and does not stop with the service contract. Instalments that extend beyond the horizon are shown separately as a remaining obligation and are not part of the total. Unconditional credits reduce the total directly; a conditional cashback appears only in a separate 'with bonus' figure. Credits that fall after the horizon are not counted.
Money is handled in whole cents so that every breakdown reconciles to its total to the cent. The average monthly figure is the total divided by the number of months; multiplied back by the months it can differ from the total by a few cents because of rounding; the total is authoritative. The calculator compares cash only: no resale value, no interest, no tax, and no check of cancellation rights. Minimum-term rules differ by country; the German rules below are one example, not a universal rule.
Formula and variables
Total cost (without bonus)=one-off costs + sum of monthly prices + instalments inside the horizon − unconditional creditsTotal cost (with bonus)=total cost (without bonus) − conditional cashbackSum of monthly prices=sum over all phases of (monthly amount × months), clipped to the horizonInstalments inside the horizon=instalment × min(instalment months, horizon)Remaining instalments=instalment × max(0, instalment months − horizon) (not in the total)Average per month=total cost ÷ horizon (rounded; average × months may differ from the total by a few cents)After the last price period: unknown → no total · unchanged → x per further month · different price (+ one-off y) → x per month, y once at the switch inside the horizon- one-off costs
- handset payment or purchase price plus activation fee and shipping, paid once at the start
- monthly price
- the monthly charge as billed; for a contract the full bundle price
- promotional phase
- optional reduced price for the first months, entered as its own phase
- device instalment
- only when billed separately from the monthly price; runs over its own term
- unconditional credit
- a firmly promised credit inside the horizon; reduces the total directly
- conditional cashback
- a credit tied to conditions; counts only in the 'with bonus' figure
- horizon
- the comparison period in whole months (quick choice 12, 24, 36, or free up to 60)
Worked examples
Example 1: phone on contract versus handset bought outright + SIM-only
| Horizon | 24 months |
|---|---|
| A – one-off handset payment | €99.00 |
| A – activation fee | €39.99 |
| A – monthly price | 6 × 49.99 (promo), then 18 × 59.99 |
| A – after month 24 | price unknown |
| B – handset purchase price | €699.00 |
| B – SIM activation fee | €9.99 |
| B – SIM-only monthly price | 24 × 19.99, then continue at 19.99 |
| C – keep current phone | SIM-only only, 9.99 activation + 24 × 19.99 |
| Total cost A | €1,518.75 |
|---|---|
| Total cost B | €1,188.75 |
| New spend C | €489.75 |
| B cheaper than A by | €330.00 |
Over 24 months path A costs €1,518.75 (99 handset + 39.99 activation + 6 × 49.99 + 18 × 59.99). Path B costs €1,188.75 (699 purchase price + 9.99 activation + 24 × 19.99), which is €330.00 less than A on the figures entered. Path C is an extra option: keeping your phone and paying SIM-only only comes to €489.75, the extra spend for a new handset versus carrying on with the old one. All figures are example assumptions.
Example 2: a device instalment running beyond the horizon and a conditional cashback
| Horizon | 24 months |
|---|---|
| A – SIM-only monthly price | 24 × 19.99 |
| A – device instalment (separate) | 36 × 20.00 |
| A – conditional cashback | 60.00 in month 3 |
| B – handset purchase price | €759.00 |
| B – SIM-only monthly price | 24 × 14.99 |
| Total cost A without bonus | €959.76 |
|---|---|
| Total cost A with bonus | €899.76 |
| Remaining instalments after month 24 | €240.00 |
| Total cost B | €1,118.76 |
Path A: a 24 × 19.99 plan (€479.76) plus a separate device instalment of 36 × 20. Within the horizon 24 instalments are paid (24 × 20 = €480.00), for €959.76 together. The remaining 12 instalments fall beyond month 24: €240.00 stay as an open obligation and are not part of the total. The 60 cashback is tied to conditions and appears only in the 'with bonus' figure: €899.76. Path B costs 759 handset + 24 × 14.99 = €1,118.76. All figures are example assumptions.
Assumptions
- All prices, phases, fees, instalments and credits are your inputs or clearly marked example assumptions, not market prices and not live tariffs.
- Prices do not fall by themselves after the minimum term; for the time after the listed months, only what you enter as 'continue at …', 'switch to …' or 'unknown' applies.
- A separately billed device instalment runs independently of the monthly price and may extend beyond the comparison horizon.
- A conditional cashback counts only in the 'with bonus' figure, because its payout is tied to conditions.
- Path C (keeping your current phone) is a separate decision aid and is not ranked against A and B as if an old handset were equivalent to a new one.
Limitations of this calculator
- The calculator compares cash flows only (pure cash outlay): no handset resale value, no interest or APR, no tax.
- No live tariffs, no provider or handset recommendation, no network-quality rating, no affiliate links.
- It does not check cancellation rights and does not model a contract extension; a separately financed instalment (its own instalment or credit agreement) may follow its own terms; check your documents.
- Qualitative differences such as data allowance, network and speed are not priced; the comparison stays a calculation on the figures you entered.
Frequently asked questions
What happens after the minimum term?
That depends on your contract and on the country. In Germany, for example, the initial term of a consumer contract may be at most 24 months, and the provider must also offer a plan with an initial term of at most 12 months (§ 56 TKG); after a tacit extension the contract can be terminated with one month's notice, at no cost arising from that termination. This calculator does not check cancellation rights and does not model an extension: for the time after the listed months you decide whether the price is unknown, stays the same or changes.
Why would I separate the device instalment from the monthly price?
Some offers bill the handset as its own monthly instalment rather than inside the plan price. Only then do you enter it as a separate device instalment. It runs over its own term and does not stop with the service contract. If the handset is already included in the monthly price, leave the field empty so nothing is counted twice. A separately financed instalment may follow its own agreement; check your documents.
How is a cashback treated?
A firmly promised credit reduces the total directly. A cashback that is tied to conditions (for example sending proof within a deadline) appears only in a separate 'with bonus, if the conditions are met' figure. That way you see both cases without an uncertain amount flattering the headline total. Credits that fall after the comparison horizon are not counted at all.
What does the average monthly figure mean?
It is the total divided by the number of months and is labelled as an average. Because it is rounded to the cent, the rounded average times the months can differ from the total by a few cents. The total, which reconciles to the cent from the individual items, is always the figure that counts.
Can I keep my current phone?
Yes. Path C works out what a SIM-only plan alone costs if you keep your current handset. It is deliberately not ranked against A or B as if an old phone were equivalent to a new one. Instead the calculator shows the extra spend for a new device versus carrying on; the decision stays yours.
Does the calculator name specific tariffs or providers?
No. There are no live tariffs, no provider or handset recommendation and no affiliate links. You enter the figures from your own offers; the contract summary you receive before signing states prices, term and the conditions for extension and cancellation. The result is cheaper only on the figures you entered.
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Sources and further reading
Official and independent sources on this topic. The links open each website in a new tab; no content is loaded from them into this page.
- § 56 TKG – contract term and termination after a tacit extensionFederal Ministry of Justice (gesetze-im-internet.de)German rule (one example): the initial term of consumer contracts is at most 24 months; a plan with an initial term of at most 12 months must also be offered; after a tacit extension, termination with one month's notice must not cause costs.
- Consumer portal – telephone and internet contractsBundesnetzagentur (German regulator)The same 24/12-month rules in Germany; before signing the provider provides a contract summary with prices, term and extension/cancellation conditions; the term may only be extended for added services or devices with the customer's express agreement.
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Last reviewed: 21/10/2026 · All calculations run in your browser – inputs are not stored. ·How we check our calculators