The RPE Calculator takes one set of data — weight, reps, and RPE — and turns it into an estimated one-rep max, a full chart of working weights, training prescriptions, and fatigue-set recommendations. This guide walks through every feature with real numbers so you can get the most out of the tool.

Step 1: Enter your top set

Your “top set” is the heaviest or most meaningful set from your session — usually the first working set, a planned single, or whatever set best represents your strength today.

A good top set for calculator purposes has three qualities:

  1. Honest RPE rating — you genuinely assessed how many reps were left.
  2. Clean technique — the set was performed with your normal competition-standard form.
  3. Low-to-moderate rep range — sets of 1–6 reps produce the most reliable e1RM estimates. Above 8 reps, accuracy decreases for all formulas.

Example: You squat 140 kg for 5 reps and it felt like RPE 8 (two reps left in the tank).

Enter into the calculator:

  • Weight: 140
  • Reps: 5
  • RPE: 8
  • Lift name: squat

The lift name is used for tracking — it lets the calculator save your e1RM history separately for each lift.

Step 2: Read your e1RM

The calculator instantly computes your estimated one-rep max using the RPE percentage table. The formula is straightforward:

e1RM = weight / percentage

For 5 reps @RPE 8, the percentage factor is 0.811 (meaning 5 reps @8 corresponds to approximately 81.1% of your max).

e1RM = 140 / 0.811 = 172.6 kg

This number represents what you could theoretically lift for a single rep at maximum effort (RPE 10) based on today’s performance. It’s the anchor for everything else the calculator produces.

Why this matters: Your e1RM is not a static number — it fluctuates day to day based on fatigue, sleep, nutrition, and stress. That’s the point. Tracking it over weeks reveals your true strength trend, independent of any single good or bad day.

Step 3: Read the output chart

The output chart is a grid showing estimated weights for every combination of RPE (10 down to 6.5) and reps (1 through 10). Each cell answers the question: “Based on today’s e1RM, what weight should I use for X reps at Y RPE?”

The chart is organized with:

  • Rows: RPE values from 10 (hardest) to 6.5 (easiest)
  • Columns: Rep counts from 1 to 10

Your entered set is highlighted in the chart. Everything else is derived from the same e1RM using the percentage table.

How to use it: If your coach prescribes “4×3 @RPE 8,” find the cell at row 8, column 3. That’s your target weight. The chart does the math so you don’t have to calculate percentages between sets.

The weight increment setting (default 2.5 lb or kg) rounds all chart values to the nearest plate-loadable weight. Adjust this to match your gym’s smallest available plates — 1.25 kg for metric microloading, 5 lb if you only have standard plates.

Step 4: Use the prescriptions table

Below the chart, the prescriptions table focuses on the most common training ranges: 3–10 reps at @7, @8, and @9. This is a quick-reference for coaches and athletes who prescribe volume work in these zones.

Example: Your e1RM is 172.6 kg. The prescriptions table shows:

Reps@7@8@9
5130.0135.0140.0
3142.5147.5152.5

So for backoff sets of 5 reps @RPE 7, you’d load approximately 130 kg. For heavier triples @9, about 152.5 kg.

Step 5: Plan fatigue and backoff sets

The fatigue section lets you estimate how much to reduce weight for subsequent sets. The idea is simple: after a hard top set, your capacity drops slightly for each additional set due to accumulated fatigue.

The calculator defaults to 4% and 6% fatigue drops, which are common starting points. If your top set was 140 kg at RPE 9:

Fatigue set 1: 140 × (1 - 0.04) = 134.4 kg
Fatigue set 2: 140 × (1 - 0.06) = 131.6 kg

When to adjust fatigue percentages: If you consistently find that your second and third sets feel much harder than expected, increase the fatigue percentage. If they feel too easy, decrease it. Most lifters settle somewhere between 3–7% depending on the lift and their conditioning.

Step 6: Track lifts over time

Every time you enter a set, the calculator saves the e1RM for that lift name and date in the Your Lifts section. Over time, this builds a history with a sparkline graph showing your e1RM trend.

This is one of the most valuable features for long-term programming. A rising sparkline means your strength is trending upward. A flat line suggests you’ve plateaued and may need to adjust training variables. A declining trend can signal overtraining, under-recovery, or the need for a deload.

Tips for tracking:

  • Use consistent lift names (e.g., always “squat” — not “back squat” one day and “squat” the next).
  • Enter your best set of the day, not every set.
  • Track across training blocks to see how different programming approaches affect your trend.
  • Use the “Add custom lift” feature for variations like “pause squat” or “close grip bench.”

The Clear lift history button removes all saved data. This is permanent — the data is stored only in your browser’s localStorage and cannot be recovered once cleared.

Step 7: Use your profile for speed

Open the Your Profile panel (person icon in the header) to save your default settings:

  • Units: Imperial (lb) or Metric (kg) — affects all calculators site-wide.
  • Bodyweight: Auto-fills calculators that need it (Wilks/DOTS, BMI, macros).
  • Weight increment: Sets the rounding increment for the RPE chart. If you set this to 2.5 in your profile, every calculator that rounds weights will use that value.

Profile data is saved locally on your device. No account required, no server involved.

Advanced mode: multiple sets

Check the Advanced: Enter Multiple Sets checkbox to unlock a grid where you can enter weights for multiple RPE/rep combinations. The calculator takes the highest e1RM from all entered sets — useful when you’ve done several working sets and want the most accurate estimate from the best one.

This is particularly helpful for sessions where you did both heavy singles and moderate-rep work. Enter the single @9 and the set of 5 @8, and the calculator uses whichever produces the higher e1RM.

Tips for getting the most out of the calculator

  • Be honest with your RPE ratings. The calculator is only as accurate as your input. If you consistently rate sets too low (calling RPE 9 sets “RPE 7”), your e1RM will be artificially inflated and your prescribed weights will be too heavy.
  • Use the Share/Screenshot features to save and share your chart. The Share button uses your device’s native sharing (or downloads a PNG if sharing isn’t available). Great for sending to a coach or training partner.
  • Check your e1RM against reality. If the calculator says your squat e1RM is 200 kg but you’ve never squatted above 180, your RPE rating was likely too low for the set you entered. Recalibrate.
  • Combine with other guides: Read What is RPE? to understand the scale in depth, and Autoregulation in Strength Training to see how RPE fits into a full training framework.