The 4% rule spends the same amount every year, raised with inflation, whatever markets do. Guardrail rules such as Guyton-Klinger let spending move: cut 10% after bad stretches, raise it after good ones. The usual claim is that this flexibility lets you start higher. It does, by a lot. But the more useful question is what you get to spend ten and twenty years later.
Here are both, run through Retirement Lab's engine, 10,000 simulated futures for every starting rate.
Try it
Guardrails vs fixed spending
Slide the starting withdrawal rate for a guardrail plan and watch what it lets you spend each year, next to a fixed plan. Hover the chart for any age.
Years it has to last
Guardrail raises
Compare with fixed spending at
Guardrails at 5.50%: lasts to 90
92%
starts at 3,670 a month; 16% of futures never cut
Fixed at 3.50%: lasts to 90
91%
2,330 a month every year, until the money runs out
| Per month at age | 60 | 70 | 80 | Money runs out |
|---|---|---|---|---|
| Guardrails, typical | 3,670 | 3,300 | 2,420 | 8% |
| Guardrails, bad case | 3,670 | 2,160 | 1,830 | |
| Fixed | 2,330 | 2,330 | 2,330 | 9% |
Free, no account needed. Opens the fixed plan. Guardrails are a Pro strategy: switch to them under Spending to compare on your own numbers.
Retirement Lab engine, 10,000 simulated futures per setting, retiring at 60 with a plan to age 90, no pension. 60% stocks / 40% bonds, Balanced outlook (stocks 8%, bonds 4.5% a year, inflation 2%). Spending per month after a 20% tax, in today's money. Guardrails cut 10% when the withdrawal rate rises 20% above its start (raise 10% when it falls 20% below, if raises are on) and never go below half the starting amount. Shaded band: 1 future in 10 spends less, 1 in 10 more. Results, not advice.
How much higher you can start
The highest starting withdrawal rate that still lasted to 90 in 90% of futures (1 million, 60% stocks, no pension, Balanced outlook):
| Retirement length | Fixed spending | Guardrails | Starting spending, fixed vs guardrails (per month, after tax) |
|---|---|---|---|
| 25 years | 4.00% | 6.25% | 2,667 vs 4,167 |
| 30 years | 3.50% | 5.50% | 2,333 vs 3,667 |
| 35 years | 3.25% | 5.00% | 2,167 vs 3,333 |
Over 30 years, guardrails start with about 57% more to spend for the same chance of the money lasting. That is the headline you will read in most articles, and it is true.
What happens to that spending later
The same two plans, 30 years, 1 million, 90% chance of lasting. Spending per month after tax, in today's money:
| Year 1 | After 10 years, typical | After 20 years, typical | After 20 years, bad case (1 in 10) | |
|---|---|---|---|---|
| Fixed at 3.5% | 2,333 | 2,333 | 2,333 | 2,333 |
| Guardrails at 5.5% | 3,667 | 3,300 | 2,420 | 1,833 |
Guardrails front-load your retirement. You spend much more in your 60s and early 70s, when most people want to travel and are able to. By year 20 the typical guardrail plan is spending about what the fixed plan spent all along, and in a bad run it has hit its floor at half the starting amount, below the fixed plan. Only 16% of futures got through 30 years without a single cut.
Whether that is a good trade depends on you. If your spending naturally falls with age, it fits well. If most of your budget is fixed costs, a cut to half is hard to live with.
Guardrails cut even when the plan is safe
The guardrails are set relative to your starting withdrawal rate, not to a safe level. A cut comes when the rate rises 20% above where it started, which happens whenever your savings fall about 17% behind inflation. That is an ordinary bear market.
So even a cautious plan gets cut. Starting at 3% over 30 years, the money lasted in practically every future, yet more than half of the futures had at least one cut, and in 1 in 10 spending was 27% below the start after ten years. If you plan to start low, a fixed rule may give you a steadier income for almost the same safety.
Raises: same safety, more spending
Retirement Lab's guardrails make no raises by default, the cautious choice. Guyton and Klinger's original rules also raise spending 10% when the withdrawal rate falls 20% below its start. In these simulations, raises did not change how often the money lasted, and they gave back part of the cuts:
| 30 years, starting at 5.5% | Lasts to 90 | After 20 years, typical | Never cut |
|---|---|---|---|
| Guardrails, no raises | 92% | 66% of start | 16% |
| Guardrails, 10% raises | 92% | 71% of start | 5% |
The trade-off is a bumpier income: more raises also means more cuts, and fewer futures without any cut.
The 4% rule, with and without guardrails
At exactly 4% over 30 years, the comparison flips from "spend more" to "worry less":
- Fixed: lasted in 84% of futures, at a steady 2,667 a month.
- Guardrails: lasted in 99%, with typical spending still at 100% of the start after ten years and 90% after twenty. In the bad 1 in 10, spending was at the floor, half the start, by year 20.
Guardrails mostly change how a plan fails. A fixed plan keeps spending until the money is gone; a guardrail plan spends less and keeps going. Both are signals to adjust. The 4% rule calculator shows how the fixed version behaves at other rates and outlooks.
How to choose
- Start with what you need, not the highest rate. The highest starting rate buys the deepest later cuts.
- Know your fixed costs. Guardrails cut total spending. If housing and healthcare are most of it, a floor-and-ceiling rule or a pension that covers them fits better.
- Commit to the cuts. The higher starting rate is only safe if you actually cut when the rule says so.
- Mind the first decade. Most cuts come from bad markets early in retirement, the sequence-of-returns risk that any spending rule is trying to handle.
For how the rules work step by step, see Guyton-Klinger guardrails. For all four strategies side by side, see spending strategies compared.
Guardrails are a Pro strategy in Retirement Lab; fixed spending is free. Run your plan with fixed spending first, then compare.
Frequently Asked Questions
- Do guardrails let you spend more than the 4% rule?
- At the start, yes. Over 30 years with a 60/40 portfolio and no pension, fixed spending reached a 90% chance of lasting at a 3.5% starting withdrawal; Guyton-Klinger guardrails reached it at 5.5%. That is about 57% more income in the first years. The price is that guardrail spending falls after bad markets, so later in retirement it is often back near the fixed amount.
- How much do guardrails cut spending in a bad market?
- Each cut is 10%, and cuts can repeat. Starting at 5.5% over 30 years, typical spending after 20 years was 66% of the starting amount, and in the worst 1 in 10 futures it had hit the floor of 50%. Starting lower means fewer and smaller cuts.
- Why do guardrails cut even when the plan is safe?
- The guardrails are relative to where you started, not to an absolute safe level. A cut comes when your withdrawal rate rises 20% above its starting point, which happens whenever your savings fall about 17% behind inflation. Even starting at a cautious 3%, more than half of the simulated futures had at least one cut.
- Should I use raises with guardrails?
- Raises do not change how often the money lasts in these simulations, but they give back some of the cuts: starting at 5.5% over 30 years, typical spending after 20 years was 71% of the start with 10% raises, against 66% without. The cost is a less steady income, because a raise can be followed by a cut.
Test your spending with fixed withdrawals
An example plan is filled in - change anything, then open it in the free simulator.
Opens the free simulator with these numbers filled in - check them and run it. Nothing is stored unless you create an account and save.