Realistic Day Planner (Planning-Fallacy Check)
Enter today's tasks and see if your plan actually fits. Applies your overrun percent, subtracts meetings and breaks, then names what to cut.
Today's task list
Per-task realistic time
| Task | Estimate | Realistic | Suggested cut |
|---|---|---|---|
| Ship the feature | 150m | 210m | Cut this |
| Write quarterly report | 90m | 126m | Cut this |
| Clear inbox and Slack | 60m | 84m | Keep |
| Review 4 PRs | 75m | 105m | Keep |
| Prep client deck | 60m | 84m | Keep |
5 tasks at a 40% overrun estimate needs 10h 9m, and you have 6h 30m free today. That is 3h 39m more than you have. Cut 2 tasks to fit today: Ship the feature, Write quarterly report.
Overview
A realistic day planner multiplies each task estimate by your usual overrun percent, the planning fallacy Kahneman and Tversky described in 1979, then compares that total against the hours actually free once meetings and breaks are subtracted. At a 40 percent overrun, five tasks estimated at 7 hours 15 minutes need 10 hours 9 minutes against 6 hours 30 minutes free, so the tool says cut 2 tasks.
How it works
- 1List today's tasks and your first-guess time estimate for each, in minutes.
- 2Set your usual overrun percent (default 40%), how much longer things really take than you first think.
- 3Enter your available hours today, your meeting hours, and your break minutes.
- 4Read the verdict banner: it shows the realistic hours needed against the hours actually free.
- 5If the plan overflows, check the per-task table for which rows it suggests cutting, largest first, until the day fits.
- 6Add or remove task rows as your day changes, and watch the verdict update live.
- 7Copy the verdict to paste into a note or share with whoever is asking why today is already full.
Worked example
Five tasks at a 40% overrun, against an 8 hour day
A 150 minute feature to ship, a 90 minute quarterly report, 60 minutes to clear inbox and Slack, 75 minutes to review 4 PRs, and 60 minutes to prep a client deck add up to 435 minutes of raw estimate. At a 40% overrun that becomes a realistic 10 hours 9 minutes. With 8 hours available, 1 hour of meetings, and 30 minutes of breaks, only 6 hours 30 minutes are actually free, a 3 hour 39 minute shortfall. The tool suggests cutting the 2 largest tasks, ship the feature and write the quarterly report, which brings the remaining total under 6 hours 30 minutes and makes the day fit.
Methodology & privacy
Each task's realistic time is its raw estimate multiplied by (1 + your overrun percent / 100); the default is 40%, a reasonable starting multiplier for the planning fallacy, the tendency Daniel Kahneman and Amos Tversky first described in 1979 in which people predict task duration optimistically and consistently run over. Needed hours sum every task's realistic minutes and convert to hours. Free hours are your available hours minus meeting hours minus break minutes divided by 60, a plain subtraction, so a day already consumed by meetings and breaks alone shows as negative free hours rather than a false zero. The plan fits when needed hours are less than or equal to free hours. When it does not fit, the cut suggestion removes the single largest remaining task by realistic minutes and repeats until the remaining total fits or no tasks are left, so it always shows the fewest, biggest tasks needed to make the day work, not an arbitrary trim. The 40% default is a common starting point, not a personalized measurement of your own habits; the overrun slider exists so you can raise or lower it once you know your own track record of running over or under.
- Source: "How do you manage time blindness?" (r/ADHD)
- Source: "You are probably overestimating the amount of tasks you can do in a day" (r/productivity)
- Source: Planning fallacy (Wikipedia), on Kahneman and Tversky's 1979 term and its measured effect sizes
Every task name, estimate, and hour you enter stays in your browser. There is no upload, no account, and no server call; the verdict exists only on your screen, and nothing is saved unless you copy it yourself.
FAQ
Why do I always overestimate what I can get done in a day?
+
This is the planning fallacy, a term Daniel Kahneman and Amos Tversky introduced in 1979 for the tendency to predict task duration optimistically even when past experience says otherwise. It is not a personal failing; it is a well-documented, near-universal bias, which is exactly why an overrun multiplier applied to your own estimates catches what your gut feeling misses.
Why do I underestimate how long tasks take?
+
People tend to picture the best-case path for a task (no interruptions, no surprises) rather than the average case, and that best-case picture is what gets estimated. A classic study found psychology students predicted 33.9 days to finish a thesis but averaged 55.5 days actually finishing it, about 64% longer. Applying a personal overrun percent to your raw estimate is a simple correction for that same gap.
What is time blindness and how does it relate to overbooking my day?
+
Time blindness is difficulty sensing how much time a task will take or how much has already passed, common in ADHD but not exclusive to it. It shows up as the same daily pattern: an achievable-looking task list that quietly needs more hours than the day has. This tool does not diagnose or treat time blindness; it just runs the arithmetic your own sense of time may be skipping.
How do you make a realistic to-do list?
+
List every task with its raw time estimate, then multiply by an overrun percent that reflects how long things actually took you before, not how long you hope they take. Subtract real meeting time and break time from your available hours to get what is actually free, then compare the two totals. If the list does not fit, cut the largest tasks first rather than trimming a little off everything.
What is the planning fallacy?
+
It is the tendency, named by Kahneman and Tversky in 1979, for people to underestimate how long a task will take, even while knowing that similar tasks took longer in the past. It affects individual to-do lists and large institutional projects alike, and simply knowing about it does not make it go away, which is why building the overrun multiplier into the arithmetic helps more than willpower does.
Can this plan my day automatically instead of me typing in every task?
+
No, this planner only works from the tasks and hours you type in; it does not read your calendar or task manager. Typing today's plan in by hand is the manual version of what recal, a local-first Mac assistant, can eventually help observe and estimate automatically on device, with your approval.
Related tools
Context-Switching Cost Calculator
Calculate how many hours and how much money context switching costs you per day, week, and year, from your interruption count and refocus time.
True Meeting Cost Calculator (with refocus tax)
Calculate what a meeting really costs: attendees times rate times duration, plus the refocus tax everyone pays after, annualized by recurrence.
Is It Worth Automating? ROI Calculator
Find out if automating a task is worth the build time. Enter your frequency, savings, and build hours for a break-even point and a clear verdict.
Downloads Folder Analyzer: Clean Up Downloads on Mac
See what is actually clogging your Downloads folder: type breakdown, biggest files, screenshot piles, old files, and duplicates. Runs entirely in your browser.
This tool fixes one moment. recal handles the whole day.
recal is a private brain for your Mac. It watches how you work, on device, and starts doing your busywork itself. You approve every action.
Get early access