When Will I Have Enough Bitcoin to Retire? HODL & Borrow Simulator
A Bitcoin retirement plan can look compelling in a spreadsheet because it combines an asset with historically high volatility and growth with the ability to borrow against collateral rather than sell it. The same features can also make the strategy fragile: a large drawdown can increase loan-to-value ratios very quickly, borrowing costs compound, and forced liquidation can crystallise losses at the worst possible time.
The calculator below does not assume that Bitcoin will continue its historic returns. Instead, it lets you stress-test your own growth, inflation, interest-rate, spending and crash assumptions. It also models a simplified UK Capital Gains Tax cost when BTC has to be sold, using an editable CGT rate and annual exempt amount.
What the strategy is actually testing
The basic idea is to hold Bitcoin as the long-term asset, borrow against part of its value to fund spending and sell BTC only when borrowing capacity is insufficient. If Bitcoin grows faster than spending and borrowing costs over a long period, the strategy can appear sustainable. If returns disappoint or a major drawdown occurs early, the same leverage can magnify the damage.
This is therefore better viewed as a sequence-of-returns and leverage stress test than as a prediction. The model is useful for asking questions such as “what happens if BTC falls 60% in year three?”, “how sensitive is the plan to an 8% borrowing rate?” or “how much BTC would have to be sold if living costs rise faster than expected?”
Borrowing against Bitcoin: the main risks
Loan-to-value and liquidation
Loan-to-value is the loan balance divided by the market value of the collateral. A 20% starting LTV can become approximately 50% if the collateral price falls by 60% before allowing for interest, so a low initial LTV does not remove liquidation risk. Platforms also use their own collateral factors, margin-call processes, liquidation thresholds and penalties.
The calculator therefore separates a target LTV from a liquidation-warning LTV. The target is the level the model tries to restore after funding each year's spending, while the liquidation-warning level tests whether a price fall and accumulated interest would put the position in danger before that rebalancing can take place.
Interest and platform risk
Borrowing costs compound when interest is capitalised rather than paid. A strategy that works at 5% borrowing may fail at 10%, even with the same Bitcoin return assumption. Variable borrowing rates can also rise exactly when market liquidity is under pressure.
There is also counterparty, custody, smart-contract and operational risk. A model that assumes you can always refinance or withdraw collateral on demand can be misleading if a lender freezes withdrawals, changes collateral requirements or a protocol fails.
UK tax: selling and using BTC as collateral
For 2026/27, individuals generally pay Capital Gains Tax at 18% or 24% on taxable gains depending on their taxable income and available basic-rate band. The annual exempt amount is £3,000. Disposing of cryptoassets for sterling, another token, goods or services can create a chargeable disposal, subject to the detailed pooling and matching rules.
Borrowing money is not itself a capital gain, but the treatment of the crypto collateral needs separate attention. Under HMRC's current 2026/27 guidance, transferring tokens into a DeFi arrangement can itself amount to a disposal if beneficial ownership passes to the platform. HMRC has announced legislation intended to introduce a no-gain/no-loss regime for qualifying cryptoasset loan and liquidity-pool arrangements from 6 April 2027, so the tax treatment of collateral arrangements is an area where the contract terms and effective date matter.
Do not assume that “borrowing against BTC is tax free” means the collateral transfer itself is always tax neutral. For 2026/27, HMRC says beneficial ownership is relevant to whether a DeFi collateral transfer is a disposal. The new no-gain/no-loss rules announced in July 2026 are intended to take effect from 6 April 2027.
Bitcoin Retirement Stress-Test Simulator
The simulator starts year one at the BTC price you enter rather than applying a year's growth before the first withdrawal. From year two onward, the growth assumption is applied before that year's spending, and any selected one-off crash is then applied in the chosen year. Existing loan interest is capitalised before the LTV check.
For each year, the model first checks whether the position has already reached your liquidation-warning LTV. If it has not, it uses the minimum BTC sale needed to keep the end-of-year loan at or below your target LTV, with the balance of that year's spending funded by borrowing. If a BTC sale raises more cash than that year's spending, the surplus is used to reduce the loan. The visual chart then shows how collateral value, loan balance and net worth evolve over time, which makes it much easier to spot when the strategy starts to wobble.
Bitcoin Retirement Stress Test
How to use the result
Do not focus only on the ending net-worth number. The most useful outputs are the peak LTV, the years in which BTC must be sold and whether a crash pushes the model close to the lender's liquidation threshold. A strategy can finish with a high theoretical net worth and still be impractical if it would have breached collateral requirements earlier in the path.
Run pessimistic cases as well as optimistic ones. Lower the growth rate, bring the crash forward, increase borrowing costs and raise spending inflation. If the plan only survives under favourable assumptions, that is useful information in itself.
Common mistakes
Treating a low starting LTV as a guarantee against liquidation
Applying CGT to the whole sale proceeds
Assuming all crypto collateral arrangements are tax neutral
Conclusion
A Bitcoin-backed retirement plan is highly sensitive to assumptions about returns, borrowing costs, inflation and the timing of market drawdowns. Borrowing can defer the need to sell assets, but it introduces leverage and counterparty risk and does not remove the need to understand the tax treatment of collateral and eventual disposals.
The simulator is most useful as a failure test rather than a forecast. If a plan remains workable after lower growth, higher interest rates and a severe early crash, that tells you more than a single optimistic compound-growth projection.
