Mark B · seam allowance
Seam allowance: the hours around the hours
Every sewing pattern adds a margin outside the line that will actually be seen. It is usually a centimetre or so, and it exists because fabric frays, seams need room and nothing is cut perfectly. A piece cut without it comes out too small.
Side work has a seam allowance too. A small design job is described as "about four hours", but those four hours sit inside a wider band: reading the brief, the back-and-forth of messages, setting up files, a second round of changes, sending an invoice, chasing it, recording it for tax purposes. Selling unused items online looks like a matter of minutes per listing until photographs, measurements, questions from buyers, packaging and a trip to the post office are counted. The visible task is the line; the allowance is everything around it.
Why the allowance gets left off
There is a well-studied reason estimates come out short. In 1979, Daniel Kahneman and Amos Tversky described what they called the planning fallacy: a tendency to predict how long a task will take by imagining the task itself, step by step, while neglecting how long similar tasks took in the past.
The best-known test came from Roger Buehler, Dale Griffin and Michael Ross in 1994. They asked university students to predict when they would finish their senior theses. The students' average estimate was about 34 days; the average actual time was about 55 days. Fewer than a third finished by the date they had predicted. In follow-up studies the same researchers found that people were quite accurate about how long other people's tasks would take, and that asking them to recall their own past projects did little to correct their estimates unless they were explicitly prompted to connect the past to the new prediction.
The planning fallacy concerns how people estimate. It does not say how long any particular piece of side work takes, which varies widely by task, platform and person.
Limits of the research
Most planning fallacy studies used students, academic tasks or short laboratory exercises, and those settings differ from paid side work with a client or a platform on the other end. A 2005 review in Psychological Bulletin by Michael Roy, Nicholas Christenfeld and Craig McKenzie argued that part of the effect may come from people misremembering how long past tasks took, rather than from optimism alone, and noted that for some very short tasks people overestimate instead. The direction of the error is fairly consistent for longer, multi-step work, but its size is not.
Counting the allowance
The research points to one practical habit, sometimes called taking the "outside view": estimating from records of similar past tasks rather than from an imagined walkthrough of the new one. For side work, that means keeping a simple log of every minute connected to a job, including the minutes that do not feel like work: replying to messages, travel, admin, fixing errors. After a few jobs, the ratio between the visible task and the total band becomes a number based on records rather than hope.
Fees belong in the same band. Platform commissions, payment processing charges, transport, materials and any tax obligations all reduce what remains from a given number of hours. They differ by country and platform, and the rules change, so Dartfold does not publish figures for them. A qualified accountant or the platform's own published terms are the right sources.
A seam allowance is not a sign that the pattern is wrong. It is the part that makes the finished piece fit.
- Kahneman, D., & Tversky, A. (1979). Intuitive prediction: Biases and corrective procedures. TIMS Studies in Management Science, 12, 313–327.
- Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the "planning fallacy": Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67(3), 366–381.
- Roy, M. M., Christenfeld, N. J. S., & McKenzie, C. R. M. (2005). Underestimating the duration of future events: Memory incorrectly used or memory bias? Psychological Bulletin, 131(5), 738–756.