Both Backdoor Roth Calculator and Mega Backdoor Roth sit in the Investing & FIRE category. They share an underlying model (pro rata rule check then conversion) but target different outcomes: Backdoor Roth on one side, Mega Backdoor Roth on the other.
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Backdoor Roth Calculator computes backdoor roth directly in your browser. It is built for roth contributions above the income limit and uses pro rata rule check then conversion based on the inputs you provide.
Mega Backdoor Roth computes mega backdoor roth directly in your browser. It is built for high earners maxing the 70k 415(c) limit and uses after tax contribution then in plan conversion based on the inputs you provide.
| Attribute | Backdoor Roth Calculator | Mega Backdoor Roth |
|---|---|---|
| Category | Investing & FIRE | Investing & FIRE |
| Primary input | Non-deductible IRA contribution, conversion timing | After tax 401(k) contribution, return, conversion frequency |
| Primary output | Tax owed on conversion, Roth balance built | After tax Roth balance built outside the 23k cap |
| Math model | Pro rata rule check then conversion | After tax contribution then in plan conversion |
| Best for | Roth contributions above the income limit | High earners maxing the 70k 415(c) limit |
| Runs in browser | Yes, no data leaves your device | Yes, no data leaves your device |
| Login required | No | No |
| Cost | Free | Free |
Under the hood, Backdoor Roth Calculator uses pro rata rule check then conversion fed by non-deductible ira contribution, conversion timing. Mega Backdoor Roth uses after tax contribution then in plan conversion fed by after tax 401(k) contribution, return, conversion frequency. The two are not substitutes; they answer adjacent questions in your workflow.
Pick Backdoor Roth Calculator when your question is about backdoor roth and your inputs are non-deductible ira contribution, conversion timing. Pick Mega Backdoor Roth when the question shifts to mega backdoor roth and your inputs become after tax 401(k) contribution, return, conversion frequency. If neither matches what you need, the Investing & FIRE category hub lists every tool we have for related questions.
Your task is long horizon planning and retirement targets and you already have contribution, return, time horizon, inflation. The output you need is a future value, withdrawal amount, retirement age.
Your task is long horizon planning and retirement targets and you have contribution, return, time horizon, inflation. The output you need is a future value, withdrawal amount, retirement age.
Browse the Investing & FIRE hub for related tools, or the Investing & FIRE hub for the other side.
Backdoor Roth Calculator is designed to answer questions about backdoor roth using non-deductible ira contribution, conversion timing. Mega Backdoor Roth is designed for mega backdoor roth using after tax 401(k) contribution, return, conversion frequency. They are complementary tools that target different inputs and outputs.
Use Backdoor Roth Calculator when your task is roth contributions above the income limit and you need a tax owed on conversion, roth balance built from non-deductible ira contribution, conversion timing.
Use Mega Backdoor Roth when the question is high earners maxing the 70k 415(c) limit and your inputs are after tax 401(k) contribution, return, conversion frequency. The result is a after tax roth balance built outside the 23k cap.
Yes. Both run entirely in your browser, require no login, and are free to use without limits. Your inputs are not transmitted to any server.
Accuracy depends on the inputs you provide, not on the tool. Backdoor Roth Calculator uses pro rata rule check then conversion and is accurate for backdoor roth when its inputs are correct. Mega Backdoor Roth uses after tax contribution then in plan conversion and is accurate for mega backdoor roth under the same condition.