A realistic timeline, set by the bird
There is no honest fixed number. A young, curious bird may be eating pellets confidently within a few weeks, a typical adult seed-eater takes one to three months of steady work, and an older bird who has eaten seed for years can take considerably longer, with plateaus where nothing seems to change for a fortnight. Anyone promising a full conversion in a set number of days is selling something. What you control is the method and the monitoring; the bird controls the calendar, and a conversion done at his pace sticks, while a rushed one usually collapses the first week you stop watching.
Plan for the long version and be pleasantly surprised, rather than expecting the short one and giving up at week three — which is, not coincidentally, where most conversions are abandoned, often just before the bird turns the corner.
The gradual method that protects his weight
Start by mixing a small share of pellets into his familiar seed — roughly a quarter pellets to three quarters seed — in the usual bowl, so he meets them constantly while still eating safely. Every week or so, shift the balance a little further toward pellets, holding each stage until you see pellet crumbs and dust in the bowl and his weight stays steady. Serve the day's freshest, most pellet-heavy portion in the morning when hunger is strongest, and keep some seed available later in the day during the middle stages so a hesitant bird never faces an all-or-nothing bowl.
Tricks that genuinely help at stubborn stages: moistening pellets so they soften toward a texture closer to soaked seed, crumbling them over foods he already likes, grinding a little pellet into a powder dusted on wet vegetables, eating a pellet-sized piece of safe food yourself in front of him, and trying a different pellet size or shape — some birds accept a smaller crumble while rejecting the standard piece they must hold and bite. Change one variable at a time and give it days, not hours.
Weighing is what makes a slow conversion safe
Weigh him weekly, same time, same scale, and write it down. The scale is the difference between a patient conversion and an accidental fast, because a bird can appear to accept pellets — picking them up, crunching, dropping — while swallowing very little. A steady weight says the current stage is working; a falling weight says step back one stage, restore more seed, and slow down, without treating it as failure. Birds must never be starved onto a new diet by removing seed entirely and waiting them out; a determined bird can genuinely harm himself refusing, and smaller species have very little reserve.
If weight falls at consecutive weigh-ins despite seed being available, or he becomes quiet, fluffed, or produces scant droppings, pause the conversion and talk to an avian vet — beak pain, illness, and stress can all hide behind what looks like pickiness.
Knowing when you have actually arrived
Call the conversion done when he eats pellets readily as the base of the diet across ordinary days — not just on one hungry morning — his weight is stable at that intake, and seed has settled into its new role as a treat and training reward rather than a meal. Keep offering variety alongside: vegetables, some fruit, and occasional seed as enrichment, because pellets were never meant to be the only thing a parrot meets. When a particular stage stalls for weeks, KinsLe's Kinny can answer what you ask next about the conversion, his reply drawn from KinsLe Answers rather than general advice.