Methodology & sources

The finder maps a weight to the adult IBJJF gi divisions. The defining detail is that IBJJF weigh-ins are conducted with the athlete in the full gi, so the published division caps are gi-on weights, not bodyweight. We store the male and female adult division limits and return the lightest division whose cap the entered weight does not exceed.

Kilogram limits are treated as authoritative; pound figures are the IBJJF-published equivalents. We intentionally do not provide no-gi limits in this tool, because no-gi divisions use different caps (no kimono on the scale) and mixing them is exactly how people show up to the wrong bracket.

The planner takes current weight, target weight and days remaining, computes the total loss required and expresses it as a percentage of bodyweight lost per week. It then classifies the plan: at or below roughly 1% of bodyweight per week is treated as a sustainable range; 1–1.5% as aggressive; above 1.5% as high risk. This framing follows sports-nutrition guidance that gradual loss preserves performance and health, while rapid cuts — especially acute dehydration — carry real danger.

The tool deliberately avoids prescribing aggressive dehydration protocols. It is a safety planner that nudges toward gradual loss or competing a division up, not a crash-cut generator.

Scoring follows the IBJJF points system: takedown 2, sweep 2, knee-on-belly 2, guard pass 3, mount 4, back control with hooks 4. A submission ends the match. Each scoring position requires roughly three seconds of stabilised control to count. When time expires, points decide the match; ties break to advantages, then penalties, then referee decision. The calculator tracks all of these per athlete.

IBJJF age divisions are determined by the age an athlete reaches during the competition year, calculated as competition year minus birth year — not age on the day of the event. The tool applies this rule to place a birth year into Juvenile 1–2, Adult, or Master 1–7. Athletes may compete down (into Adult) but not up into an older Master bracket than their age permits.

The finder maps height and weight to a starting A-size (A0–A5, with F-sizes noted for women). Because there is no universal A-size standard — each brand publishes its own measurements — the result is explicitly a starting point to confirm against the manufacturer’s chart, with guidance on how shrinkage and build shift the choice. We do not claim a single ‘correct’ size across brands.

The estimate is driven by fabric type, wash temperature and drying method, reflecting that cotton contracts with heat — most in hot wash plus hot tumble-dry, least in cold wash and hang-dry — while pre-shrunk and ripstop fabrics move far less. Because real shrinkage depends on the specific gi, prior washing and exact blend, the output is presented as a directional guide for how to wash, not a precise final measurement.

Resting metabolic rate is estimated with the Mifflin–St Jeor equation, the best-validated of the common predictive formulas. It is multiplied by an activity factor scaled to weekly training frequency, then adjusted modestly for the stated goal (maintain, lean, gain). Macros default to roughly 2 g protein per kg bodyweight, ~25% of calories from fat, and the remainder from carbohydrate, with a sensible calorie floor. These are evidence-aligned defaults, not a personalised prescription — a registered sports dietitian should be consulted for individual plans.

The estimator anchors on IBJJF graduation system minimums — about 2 years at blue before purple, 1.5 years at purple before brown, and 1 year at brown before black, with no fixed minimum from white to blue — then layers typical progression rates by training frequency to produce a range. It is explicit that promotion is the instructor’s decision and that the minimums are floors, not expected timelines.

This tool presents general return-to-sport timeframes by injury type and severity, drawn from published sports-medicine ranges. It is educational only and explicitly not medical advice; it flags injuries that require professional management (concussion, post-surgical recovery) and conditions that mandate staying off the mat entirely until cleared (skin infections such as ringworm, staph and herpes gladiatorum). Any output is a starting point for a conversation with a qualified clinician.

The read estimates weekly training stress from session count and intensity, then compares it to a recovery capacity shaped primarily by sleep and modulated by age, returning a simple recovered / balanced / monitor / back-off judgment. It draws on the established training-stress-versus-recovery framework underpinning load monitoring in sport. It is a directional guide based on those principles, not a validated clinical instrument.

Adult match length is a published IBJJF rule keyed to belt: white 5, blue 6, purple 7, brown 8, black 10 minutes. These adult durations are consistent across the rule book and major events, so the tool returns them directly. Finals at major championships and special rulesets can differ, which the tool notes.

Masters, juvenile and kids divisions run shorter than adult, but the exact per-belt masters durations are reported inconsistently across sources and have changed between rule-book editions. Rather than publish a masters table we can’t stand behind, the tool states the direction and points competitors to the current official rule book for the precise number — we’d rather you confirm than rely on a figure that might be wrong on the day.

This tool uses the ADCC World Championship divisions: men −66, −77, −88, −99 and +99 kg; women −55, −65 and +65 kg, plus Absolute. ADCC is no-gi, so weigh-ins are in shorts and rashguard, and the championship uses a day-before weigh-in — a key difference from IBJJF’s same-day weigh-in. ADCC Opens and Trials use additional, more granular classes, so we direct competitors to the specific event rules.

BJJ belts use the same A0–A5 scale as gis, and the correct belt is the one matching your gi size. When gi size isn’t known, height is the best single predictor, which is what we map. Because there is no cross-brand standard, the output is an explicit starting point to confirm against the manufacturer’s chart — we do not claim a single correct size across brands.

This is a laundry-turnaround calculation, not a measured standard. A gi is washed after every session and must dry fully before reuse — about two days hang-drying, overnight in a dryer. We multiply weekly sessions by that turnaround and add one for margin. The underlying hygiene rule (wash every time) reflects standard grappling skin-infection guidance; the count itself is practical logic, and we label it as such.

Pure geometry. Standard EVA puzzle tiles are 1 m × 1 m, so tile count is the rounded-up square-metre coverage of your space, and cost is tiles × your price per tile. The thickness guidance — 40 mm for takedowns, 20 mm for ground work — follows common training-surface safety practice. The math is exact; the thickness advice is a general recommendation.

Energy expenditure is estimated with MET (metabolic equivalent) values from the Compendium of Physical Activities, run through the ACSM equation: kcal ≈ MET × 3.5 × bodyweight(kg) ÷ 200 × minutes. We map drilling to ~5.3 MET, steady rolling to a moderate value, and hard sparring to the vigorous martial-arts value of ~10.3 MET. Because grappling is intermittent and individual, we present the result as a ballpark, not a measurement.

The target scales the evidence-based athlete range of roughly 1.6–2.2 g of protein per kg of bodyweight per day to your weight and goal. These figures come from the ISSN and ACSM position stands on protein for active people. They are general targets for healthy adults, not a personalised prescription, and the tool says so and points to a registered dietitian for individual plans.

Sweat loss is computed the standard way: (weight before − weight after) + fluid consumed during the session = fluid lost; divided by time for an hourly sweat rate. Rehydration of ~125–150% of the loss over the following hours follows National Athletic Trainers’ Association fluid-replacement guidance. This is a recovery tool and is explicitly not for cutting weight by dehydration.

One-rep max is estimated from a submaximal set using two established formulas: Epley (1RM = w × [1 + reps ÷ 30]) and Brzycki (1RM = w × 36 ÷ [37 − reps]), averaged. Both are accurate in the low-rep range and drift above ~10 reps, so the tool caps input and recommends a heavier set for a better estimate. The percentage table (90/80/70%) reflects common strength-programming conventions.

The daily target uses a bodyweight baseline of roughly 30–40 ml per kg (inclusive of fluid from food) and adds ~0.5–0.7 L per hour of training, with a hot-climate adjustment. These are general hydration guidelines; the tool stresses that thirst and urine colour are better real-time guides, and points to the sweat-rate tool for a measured per-session figure. It is an estimate, not medical advice.